Best Practices for

Road Weather Management 

Version 3.0

June 2012
ii

 

Acknowledgments

While many individuals deserve recognition, the authors want to particularly acknowledge all the 

staff at the participating state departments of transportation who provided materials and were 

generous with their time and expertise. Any opinions, findings, and conclusions or 

recommendations expressed in this publication are those of the authors and do not necessarily 

reflect the views of the Federal Highway Administration.

Notice

This document is disseminated under the sponsorship of the U.S. Department of Transportation 

in the interest of information exchange. The U.S. Government assumes no liability for the use 

of the information contained in this document.

The U.S. Government does not endorse products or manufacturers. Trademarks or 

manufacturers’ names appear in this report only because they are considered essential to the 

objective of the document.

Quality Assurance Statement

The Federal Highway Administration (FHWA) provides high-quality information to serve 

Government, industry, and the public in a manner that promotes public 

understanding. Standards and policies are used to ensure and maximize the quality, objectivity, 

utility, and integrity of its information. FHWA periodically reviews quality issues and adjusts its 

programs and processes to ensure continuous quality improvement.
iii

Technical Report Documentation Page

1. Report No.

FHWA-HOP-12-046

2. Government Accession No. 3. Recipient's Catalog No.

4. Title and Subtitle

Best Practices for Road Weather Management, Version 3.0

5. Report Date

June 2012

6. Performing Organization Code

7. Co-Author(s)

Ray Murphy, FHWA; Ryan Swick, Booz Allen Hamilton; 

Gabe Guevara, FHWA

8. Performing Organization Report No.

9. Performing Organization Name and Address 10. Work Unit No. (TRAIS)

11. Contract or Grant No.

12. Sponsoring Agency Name and Address

Federal Highway Administration (FHWA)

Office of Transportation Operations

Washington, DC 20024

13. Type of Report and Period Covered

14. Sponsoring Agency Code

15. Supplementary Notes

16. Abstract

On average, there are over 6,301,000 vehicle crashes each year. Twenty-four (24) percent of these 

crashes – approximately 1,511,000 – are weather-related, resulting in 7,130 fatalities and 629,000 

injuries. In spite of these statistics, there is a perception that transportation managers can do little 

about weather. However, three types of mitigation measures may be employed in response to 

environmental threats: advisory; control; and treatment strategies. Advisory strategies provide 

information on prevailing and predicted conditions to both transportation managers and motorists. 

Control strategies alter the state of roadway devices to permit or restrict traffic flow and regulate 

roadway capacity. Treatment strategies supply resources to roadways to minimize or eliminate 

weather impacts. Many treatment strategies involve coordination of traffic, maintenance, and 

emergency management agencies. These road weather management strategies are employed in 

response to various weather threats including fog, high winds, snow, rain, ice, flooding, tornadoes, 

hurricanes, and avalanches. 

This report contains 27 case studies of systems in 22 states that improve roadway operations under 

inclement weather conditions. Each case study has six sections including a general description of the 

system, system components, operational procedures, resulting transportation outcomes, 

implementation issues, as well as contact information and references. Appendix A is an acronym list. 

17. Key Word

adverse weather, traffic management, emergency 

management, winter maintenance, traveler 

information

18. Distribution Statement

19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No. of Pages

92

22. Price

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized
iv

Table of Contents

Introduction................................................................................................................................ 1

Alabama DOT Low Visibility Warning System ............................................................................ 2

Alaska DOT&PF Temperature Data Probe Program .................................................................. 3

Arizona DOT DUST Warning System........................................................................................11

California DOT Fog Detection and Warning System .................................................................15

California DOT Icy Curve Warning System ...............................................................................19

Colorado DOT One Pass Clearing Operations..........................................................................23

Colorado DOT Variable Speed Management System ...............................................................27

Florida DOT Bridge Wind Speed Alerting System .....................................................................29

Idaho TD Winter Maintenance Performance System.................................................................32

Iowa DOT Salt Use Dashboard .................................................................................................34

Iowa DOT WeatherView Road Weather Traveler Information System ......................................36

Kansas City Scout Advanced Traffic Management System.......................................................38

Kansas DOT Road Weather Information for Travelers System .................................................41

Maryland DOT Emergency Truck Parking Portal.......................................................................44

Michigan DOT Measurement of Regain Time ...........................................................................47

Minnesota DOT I-35W Smart Lanes: Active Traffic Management .............................................49

Montana DOT Equipment Vehicle Management System...........................................................55

Montana DOT Traveler Information System ..............................................................................57

New Mexico DOT Dust Control System ....................................................................................58

Pennsylvania DOT Interstate Restriction System......................................................................60

South Carolina DOT Hurricane Traffic Evacuation Operations ..................................................63

South Dakota DOT Maintenance Decision Support System......................................................66

Tennessee DOT Low Visibility Warning System........................................................................69

Texas DOT High Water Detection System ................................................................................73

Texas DOT Pump Station Monitoring System ...........................................................................75

Utah DOT Traveler Information Weather...................................................................................77

Vermont Agency of Transportation: Transportation Operations Center .....................................80

List of Appendices

Acronym List.........................................................................................................................A-1
v

List of Figures

Figure AL-1 Screen shot of low visibility warning system ........................................................... 2

Figure AK-1 Thermistor string and temperature probe casing .................................................... 5

Figure AK-2 Boring hole for temperature probe.......................................................................... 5

Figure AK-3 Top sensor on a wire lead ...................................................................................... 6

Figure AK-4 Diagram on the vertical thermistor spacing............................................................. 6

Figure AK-5 Example of a posted weight restriction ................................................................... 7

Figure AK-6 Areas and corridors of Alaska with TDP sites......................................................... 7

Figure AK-7 Anchorage-Homer corridor with available TDP sites .............................................. 8

Figure AZ-1 Visibility sensor in ADOT DUST warning system ...................................................11

Figure AZ-2 Dynamic message sign with warning message......................................................12

Figure CA-1 Sensor array .........................................................................................................15

Figure CA-2 Road weather information system at Fredonyer East ICWSs................................19

Figure CA-3 Schematic of Fredonyer Pass and Icy Curve Warning System..............................20

Figure CO-1 Truck with 14 ft. wide front plow............................................................................23

Figure CO-2 Tow plow being loaded with salt ...........................................................................23

Figure CO-3 RWIS Snowmass Canyon ....................................................................................27

Figure CO-4 Alert of wet roads..................................................................................................27

Figure FL-1 FDOT bridge wind speed monitor installation.........................................................29

Figure ID-1 RWIS installation at Goose Creek Summit .............................................................32

Figure IA-1 Example screen shots from the Iowa DOT salt use dashboard...............................34

Figure IA-2 WeatherView website showing RWIS and AWOS site locations .............................36

Figure KC-1 Kansas City Scout's ATMS integrated with weather information............................39

Figure MD-1 Maryland's emergency truck parking portal...........................................................45

Figure MI-1 Speed sensor apparatus to determine regain time.................................................47

Figure MN-1 ATM signals on I-35W ..........................................................................................49

Figure MN-2 Possible display messages above traffic lanes.....................................................50

Figure MN-3 Example of display of intelligent lane control signals during an incident................51

Figure MN-4 Display of advisory speed limits on DMS as it relates to freeway speeds ............51

Figure MN-5 Static sign for dynamic shoulder lane ...................................................................53

Figure MN-6 Striping and signing with PDSL closed .................................................................53

Figure MN-7 Striping and signing with PDSL open....................................................................53
vi

List of Figures (continued)

Figure MT-1 Montana DOT EVMS main application window.....................................................55

Figure MT-2 Components of traveler information system ..........................................................57

Figure NM-1 Poor visibility of I-10 due to dust storm .................................................................58

Figure NM-2 La Playa I-10 RWIS mile post 12..........................................................................58

Figure PA-1 Interstate restriction flow chart...............................................................................61

Figure SC-1 Aerial view of I-26 near Columbia, SC where reversal is terminated .....................64

Figure SD-1 Surface conditions predicted by MDSS closely match actual road conditions .......66

Figure TN-1 Fog detector..........................................................................................................69

Figure TN-2 CCTV camera .......................................................................................................69

Figure TN-3 CSLS ....................................................................................................................69

Figure TN-4 Swing gate ............................................................................................................69

Figure TX-1 Public Internet display of TxDOT- San Antonio high water detection systems .......73

Figure TX-2 Storm water pump station......................................................................................75

Figure UT-1 Weather impact graphic from March 1, 2012.........................................................77

Figure VT-1 Traffic operations center........................................................................................80

Figure VT-2 Traffic operations center communications specialist..............................................80

Figure VT-3 Traffic operations center fiber optic project manager .............................................80

List of Tables

Table AL-1 Low Visibility Warning System Strategies ................................................................ 3

Table TN-1 Advisory and Control Strategies for Various Road Conditions ................................70
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Introduction

Weather threatens surface transportation 

nationwide and impacts roadway safety, 

mobility, and productivity. Weather affects 

roadway safety through increased crash risk, 

as well as exposure to weather-related 

hazards. Weather impacts roadway mobility 

by increasing travel time delay, reducing traffic 

volume throughput and speeds, increasing 

speed variance (i.e., a measure of speed 

uniformity), and decreasing roadway capacity 

(i.e., maximum rate at which vehicles can 

travel). Weather events influence productivity 

by disrupting access to road networks, and 

increasing road operating and maintenance 

costs. 

There is a perception that transportation managers can do little about the average 7,130 

fatalities and 629,000 injuries that occur every year during adverse weather 

conditions. However, three types of road weather management strategies may be employed in

response to environmental threats: advisory; control; and treatment strategies. Advisory 

strategies provide information on prevailing and predicted conditions to both transportation 

managers and motorists. Control strategies alter the state of roadway devices to permit or 

restrict traffic flow and regulate roadway capacity. Treatment strategies supply resources to 

roadways to minimize or eliminate weather impacts. Many treatment strategies involve 

coordination of traffic, maintenance, and emergency management agencies. These mitigation 

strategies are employed in response to various weather threats including fog, high winds, snow, 

rain, ice, flooding, tornadoes, hurricanes, and avalanches. 

This report contains 27 case studies of systems in 22

states that improve roadway operations under 

inclement weather conditions. Each case study has six 

sections including a general description of the system, 

system components, operational procedures, resulting 

transportation outcomes, implementation issues, as 

well as contact information and references. 

Version 2.0 presented 30 case studies from municipal 

and state transportation agencies. At this point, those 

solutions are either mainstreamed or have been 

surpassed by even better solutions. Version 3.0 

captures the state-of-the-art, presenting 27 all-new 

practices that build upon these agencies’ previous 

successes.
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Alabama DOT Low Visibility Warning System

In March 1995 a fog-related crash involving 193 vehicles occurred on the seven-mile (11.3 

kilometer) Bay Bridge on Interstate 10. This crash prompted the Alabama Department of 

Transportation (DOT) to deploy a low visibility warning system. The warning system was 

integrated with a tunnel management system near Mobile, Alabama.

System Components: Six sensors with forward-scatter technology are used to measure 

visibility distance. The visibility sensors are installed at roughly one-mile (1.6 kilometer) intervals 

along the bridge. Traffic flow is monitored with a Closed Circuit Television (CCTV) surveillance 

system. Video from 25 CCTV cameras is displayed on monitors in the Traffic Management 

Center (TMC). Field sensor data is transmitted to a central computer in the TMC via a fiber optic 

cable communication system. The computer controls 24 Variable Speed Limit (VSL) signs and 

five Dynamic Message Signs (DMS), which are used to display advisories or regulations to 

motorists.

In 2008, a system upgrade was performed to the fog system. These upgrades included updating 

devices, improving the method of communication with these devices by going from a point-topoint system to Ethernet, and the addition of Radar Vehicle Detection (RVD) devices every onethird of a mile along the Bayway.

Figure AL-1. Screen Shot of Low Visibility Warning System.

System Operations: At least two Automated Transportation System (ATS) Operators staff the 

TMC twenty-four hours a day. When fog is observed via CCTV, ATS Operators consult the 

central computer, which displays visibility sensor measurements by zone. The warning system 

is divided into six zones which can operate independently. Depending on visibility conditions in 
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each zone, operators may display messages on DMS and alter speed limits with VSL signs (as 

shown in the Table AL-1, Visibility Warning System Strategies).

Table AL-1. Low Visibility Warning System Strategies.

Visibility Distance Advisories on DMS Other Strategies

Less than 900 feet

(274.3 meters) “FOG WARNING” Speed limit at 65 mph (104.5 kph)

Less than 660 feet

(201.2 meters)

“FOG” alternating with 

“SLOW, USE LOW BEAMS”

“55 MPH” (88.4 kph) on VSL 

signs

“TRUCKS KEEP RIGHT” on 

DMS

Less than 450 feet

(137.2 meters)

“FOG” alternating with 

“SLOW, USE LOW BEAMS”

“45 MPH” (72.4 kph) on VSL 

signs

“TRUCKS KEEP RIGHT” on 

DMS

Less than 280 feet

(85.3 meters)

“DENSE FOG” alternating 

with

“SLOW, USE LOW BEAMS”

“35 MPH” (56.3 kph) on VSL 

signs

“TRUCKS KEEP RIGHT” on 

DMS

Street lighting extinguished

Less than 175 feet

(53.3 meters)

I-10 CLOSED, KEEP 

RIGHT, EXIT

1⁄2 MILE Road Closure by 

Highway Patrol

When the speed limit is reduced, notices are automatically faxed to the DOT Division Office, the

Highway Patrol and local law enforcement agencies in Mobile and neighboring jurisdictions (i.e., 

Daphne and Spanish Ford). If necessary, ATS Operators request that the Highway Patrol utilize 

vehicle guidance to further reduce traffic speeds. During vehicle guidance operations a patrol 

vehicle with flashing lights leads traffic across the bridge at a safe speed.

Transportation Outcome(s): Although labor-intensive, the warning system has improved safety 

by reducing average speed and minimizing crash risk in low visibility conditions.

Implementation Issues: The original system design included a vehicle detection subsystem, 

backscatter visibility sensors, and automated activation of signs. Bridge deck construction 

precluded the installation of inductive loop detectors and vibration prevented the use of 

microwave vehicle detectors. Thus, the vehicle detection subsystem had to be eliminated. 

Visibility sensors with backscatter technology were deployed along the bridge in the fall of 1999. 

However, problems with accuracy and reliability caused the DOT to replace them with forwardscatter visibility sensors in 2000. 

The original George C. Wallace tunnel control room was modified to incorporate monitoring and 

control functions for the warning system, which began operating in September 2000. By 2004, 

control of the warning system was transferred to the new Traffic Management Center.

Contact(s):

• David M. Johnson, Alabama DOT, ATS Center Manager, 251-432-4069,

johnsond@dot.state.al.us

• Daniel Driskell, Alabama DOT, Acting Traffic Engineer, 251-470-8231, 

driskelld@dot.state.al.us
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• Lee Reach, Alabama DOT, Division Maintenance Engineer, 251-470-8230,

reachl@dot.state.al.us

Reference(s):

• Schreiner, C., “State of the Practice and Review of the Literature: Survey of Fog

Countermeasures Planned or in Use by Other States,” Virginia Tech Research Council,

October 2000.

• U.S. DOT, “Mobile, Alabama Fog Detection System,” 2001 Intelligent Transportation

Systems (ITS) Projects Book, FHWA, ITS Joint Program Office.

Keywords: fog, visibility, low visibility warning system, tunnel management system, speed 

management, traffic management, law enforcement, traveler information, advisory strategy, 

traffic control, control strategy, bridge, lighting, high-profile vehicles, motorist warning system, 

closed circuit television (CCTV), dynamic message sign (DMS), institutional issues, speed, 

safety
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Figure AK-1. Thermistor string and 

temperature probe casing.

Figure AK-2. Boring hole for 

temperature probe.

Alaska DOT&PF Temperature Data Probe Program

The Alaska Department of Transportation and Public Facilities (ADOT&PF) has developed an 

effective seasonal weight restriction program that uses temperature data probe (TDP) profiles 

as one tool to issue fact-based weight restriction notices. TDP sensors deployed at strategic 

locations provide a vertical temperature profile in the six foot layer below the pavement surface. 

The TDP sites are polled periodically, data are collected and loaded into an Oracle relational 

database, and then are available under Alaska’s Road Weather (RWIS) and Temperature Data 

Profiles TDPs for M&O on the ADOT&PF internal web page <web.dot.state.ak.us> and the 

Road Weather Information System (RWIS) public web site <http://roadweather.alaska.gov>. 

Weight limitations during the spring thaw restrict the Maximum Allowable Axle or Axle Group 

Weights to less than the typical summer/winter loads. These restrictions help prevent pavement 

damage, avoid higher road maintenance costs, and limit vehicle wear and tear. Additionally, 

timely weight restriction notices allow commercial trucking the opportunity to plan their work 

schedules and minimize the impacts of hauling less than full loads.

The regional maintenance engineers base these temporary weight restrictions on the downward 

thaw progression; inputs to their decision process include:

• Past weather – includes the past week and conditions from the previous fall such as 

amount of rainfall

• National Weather Service forecasts – solar insolation, temperatures, precipitation

• Local maintenance and operations staff experience – including local TDP measurements 

• Roadway pavement structure – roadbed materials, soil characteristics, pavement age, 

and drainage capabilities

• Site observations – standing water, water seepage through pavement cracks, 

precipitation, and remaining snow cover

The weight restriction decision-making process involves multiple ADOT&PF work centers. 

Communication among state, local government, and commercial trucking agencies provide for 

an effective restriction notice distribution process.

System Components: The temperature probe program started with the Northern Region 

Fairbanks Research Section more that 20 years ago. In 1990 there was a coordinated effort to 

install statewide permanent data recorders and collect telemetry. The TDP program continues 

with new installations as construction projects and funding allows. There are over 75 sites 

around the state where TDP are installed in the road section. 
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Figure AK-3. Top sensor on a 

wire lead.

The probes have been manufactured by Measurement 

Research Corporation (MRC). MRC is only providing a 

limited number of TDP units, so ADOT&PF is diligently 

searching for another supplier for future years. Each 

probe has a lead-in data cable and a 6-foot thermistor 

string, one-inch diameter, encased in an epoxy resin. 

Figure AK-1 shows the 6-foot thermistor string with the 

top “pig-tail” thermistor featured in the inset. The MRC 

probe is installed vertically through the pavement in a 

hole, which is normally drilled through the shoulder of 

the road, as shown in Figure AK-2. The hole is backfilled with sand and capped with asphalt pavement. 

There are 16 thermistors in the MRC probe. The top 

sensor is on a wire lead and is placed within 1 inch of the pavement surface (Figure AK-3). The 

second sensor is positioned at the bottom of the pavement, no matter the depth. Sensors #3 

through #6 are spaced 3 inches apart, sensors #7 through #16 are spaced 6 inches apart, so 

sensor #16 is positioned 72 inches below the bottom of the pavement. Figure AK-4 diagrams 

the vertical thermistor spacing. The older MRC probes co-located with a RWIS site do not have 

the pavement surface thermistor. In these cases, the RWIS pavement sensor (Vaisala’s FP 

2000, ThermoScan1000, or DST 111) temperature is used for this top reading and is reported in 

the online TDP profiles.

Figure AK-4. Diagram of the vertical thermistor spacing.

The graph shows the contrast of different pavement thickness and levels of temperature measured by the MRC 

probe (installed at the bottom of pavement) vs. the SSI 17 inch probe (installed from pavement surface). Note: 

Drawing is not to scale.
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Figure AK-6. Areas and corridors

of Alaska with TDP sites.

System Operations: Regional maintenance engineers try to issue weight restrictions three days 

prior to altering existing weight restrictions to allow truck operators to plan their work schedules 

and to minimize the impacts. The regional Maintenance and Operations staff e-mails the 

restriction notices to a pre-determined list of parties, which includes ADOT&PF regions and 

districts, trucking firms, ADOT&PF Measurement Standards and Commercial Vehicle 

Enforcement (MS/CVE), the military, Alaska State Troopers, local law enforcement, and local 

transportation authorities. The local Maintenance and Operations staff post the restriction signs 

along the roadway.

Figure AK-5. Example of a posted weight restriction.

Local transportation authorities use the State restrictions to help develop local restrictions. In 

many cases, they adopt the ADOT&PF restrictions for adjacent roads in their service areas. 

Local Maintenance and Operations staff may also issue weight restrictions on State roads in 

their local area. 

MS/CVE posts the weight restrictions 

on the State of Alaska Online Public 

Notice web site 

<http://notes4.state.ak.us/pn> and 

maintains the commercial weight 

restrictions on the MSCVE web site: 
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Figure AK-7. Anchorage-Homer corridor

with available TDP sites.

<http://dot.alaska.gov/mscve/main.cfm?go=weightrestrictions>. Figure AK-5 shows an example 

of a posted weight restriction. MS/CVE Commercial Vehicles Customer Service Center posts 

the weight restrictions on FAX-On-Demand (907-348-9876). Stakeholders can also sign up for 

email and text message notification. MSCVE and the Alaska State Troopers enforce the posted 

weight restrictions.

TDP data are available on the internal ADOT&PF home page at <http://web.dot.state.ak.us/>

under Alaska’s Road Weather (RWIS) and Temperature Data Profiles TDP’s for M&O and on 

the Road Weather Information System (RWIS) public web site <http:/roadweather.alaska.gov>. 

Both web applications also include road weather and camera information. On the internal 

application, Vaisala’s proprietary ScanWeb application presents the most recent TDP for each 

site. There is also an area summary for TDP sites within a given travel corridor.

Both web sites offer access to TDP 

through corridor maps. Figure AK-6 

shows the four areas and six 

corridors that have TDP sites. 

Passing the cursor over an 

area/corridor area will highlight the 

area/corridor on the state map. 

Clicking on the area/corridor text will 

display the area/corridor with the 

available TDP sites. Figure AK-7 

shows the Anchorage – Homer 

corridor with the available TDP sites. 

Hovering over the TDP site displays 

the name of the site.

The RWIS web site 

<http://roadweather.alaska.gov>

provides Road Weather, Camera, 

and TDP information on a single 

base map. Simply click on TDP at 

the top of the corridor map to show 

the available TDP sites for this map 

area. Select the appropriate TDP site to get to the TDP setup screen. Output formats include 

both an on-line graphical report and a delimited export file. A pull-down menu also provides an 

alpha list of available TDP sites. Three time periods are available: 24 hours, 7 days, and 31 

days. A calendar function provides an easy date range selection; the earliest data availability is 

included in the site metadata. TDP data are sorted into three-degree temperature bins for 

graphical display.

Transportation Outcome(s): A progressive series of roadway weight restrictions become 

necessary each spring when Alaska’s road embankments thaw as temperatures rise from south 

to north across the state. These spring weight restrictions are necessary to help protect 

highways from unnecessary damage, help avoid higher road maintenance costs, and limit 

vehicle wear and tear.

Per the Alaska Regulations, at 17 AAC 25.100 (a), “The Department of Transportation and 

Public Facilities may prohibit the operation of vehicles upon any highway or may impose 

restrictions on any aspect of vehicle operation on any highway whenever the highway, in the 

judgment of the commissioner, may be seriously damaged or destroyed by such operation.” 
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Limitations are therefore imposed from March through June, area by area, and road by road, by 

restricting the Maximum Allowable Axle or Axle Group Weights to less than typical summer or 

winter loads. Where a value of “100%” represents the normal legal maximum allowable weight, 

key paved and unpaved roads are temporarily constrained by public legal notice to restrictions 

of 85%, 75%, or even 50% of the statutorily defined weights.

Once the thaw process starts at the pavement surface and progresses downward slowly, over a 

period of days and weeks, moisture content rises and a water-saturated layer of soil generally 

develops between the uppermost (thawed) zone of pavement and structural fill, and the stillfrozen mass of sub grade beneath the thawed layer. 

• Trucks and trailers moving heavy cargoes press down atop this constrained system, 

dramatically increasing the thaw zone’s pore pressure. This potentially can cause 

“quick” foundation conditions, a loss of strength within the granular soil matrix, and can 

trigger pavement flexure and rutting (soil displacement), constituting significant road 

damage. The real-time TDP temperature data at various depths, times of day, and 

dates provides a clear indication of when certain roads across the state are likely to be 

incapable of supporting heavy wheel loads because of the progressing thaw depth. This 

is when load limits, restricting vehicle loads to viable non-damaging levels, are posted.

Reasonable thaw progression estimates are possible by observing site-specific conditions 

reported by experienced maintenance station foremen. Considerations such as a road’s 

drainage and soil characteristic, variable pavement age and structural condition, remaining 

snow cover, and weather forecasts are all important at each TDP location. The maintenance 

engineer uses the previous years’ archived TDP thaw data and the relative loss of strength from 

shallow thaw depths to impose load limits. With the return of load-carrying ability within the 

granular embankment structure in place below the paved (or unpaved) road surface as the thaw 

gets deeper, load limits are then carefully lifted. Depending on the quality of the roadway’s 

structural regime and moisture content circumstances, load restrictions are usually completely 

lifted as the thaw depth exceeds 48 inches. 

DOT&PF’s TDP sensors play an important role in selecting which roads to include in road 

restriction notices and to what level of restriction to apply at various dates. Alaska’s costeffective TDP system plays a useful and desirable role in providing real-time temperature data 

for year-round uses, but its spring applications are particularly critical and unparalleled in 

protecting the state’s $10 billion highway infrastructure, while realistically balancing the 

competing needs of surface transportation, commerce and industrial livelihoods. TDP data are 

also used for road design and arctic research.

Implementation Issues: The TDP program incorporates two statewide networks, one for TDPs 

co-located with RWIS sites and one that is comprised of stand-alone installations. The colocated sites are polled hourly by the RWIS servers in Anchorage and Juneau and packaged 

into a 24 hour TDP data file. The stand-alone sites are polled periodically by the Central Region 

Highway Data Section (CR/HDS). TDP data are transferred to Juneau where they are loaded to 

an Oracle relational database at 5:00am, noon, and 5:00pm each day. 

Campbell Scientific data loggers (model CR-10X) installed in adjacent roadside cabinets collect 

the CR/HDS TDP data. The CR/HDS polls the TDP sites via modem periodically, more often in 

the spring, forwards hourly data files to Juneau for loading into an Oracle relational database. 

Manual readings can be taken from the remaining older MRC thermistor probes on-site when 

connected to a hand-held display. Most of the stand-alone TDP sites also have other 

temperature sensors installed such as ambient air temperature and the reference temperature 
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inside the control cabinet. These additional data elements are also available in the Oracle 

database. 

The MRC probes co-located with RWIS sites are connected to the RWIS remote-processing unit 

(RPU) computer in adjacent roadside cabinets. Vaisala, the Department’s RWIS contractor, 

maintains the RWIS sites. These sites are equipped with telemetry that ties into the Internet or 

the State of Alaska wide area network (WAN). At remote locations, wireless radios provide a 

connection from the RWIS sites to the Internet or WAN. The RWIS servers in Anchorage and 

Juneau poll these sites at least three times an hour. The RWIS server forwards the daily TDP 

files to Juneau for loading into the Oracle relational database.

ADOT&PF has several ongoing initiatives to upgrade the RWIS web site and TDP program. 

These initiatives include moving to a GIS-enabled, Google-like web interface, improving the 

communications to the CR/HDS TDP data loggers, automate the CR/HDS TDP data polling, 

and introduce standard TDP profile reports that can be distributed to interested stakeholders 

automatically. 

Contact(s): 

• Howard Helkenn, Central Region Traffic Data Manager, 907-269-0876, 

howard.helkenn@alaska.gov

• Jack Stickel, Transportation Information Group – Division of Program Development, 907-

465-6998, jack.stickel@alaska.gov

Reference(s): 

• Road Weather Information System (RWIS) public web site 

<http://roadweather.alaska.gov>

• State of Alaska Online Public Notice web site <http://notes4.state.ak.us/pn>

Keywords: legal maximum allowable weight, maximum allowable axle weights, quick foundation 

conditions, seasonal weight restrictions, spring weight restrictions, soil temperature profiles, 

spring thaw, temperature probes, temperature data probes
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Arizona DOT DUST Warning System

One of the biggest challenges for road weather management along Interstate 10 (I-10) is dust 

storms. Currently, in the spring of each year these often unpredictable events wreak havoc on 

travel along I-10. Dust storms are an important safety concern in the region, especially for outof-state drivers who are unfamiliar with this phenomenon. These dust storms can reduce 

visibility to extremely low levels, causing multiple-car accidents.

The Arizona Department of Transportation (ADOT) has developed the Dual Use Safety 

Technology (DUST) Warning System to help reduce the loss of life, injury, and property damage 

on rural I-10 in Cochise County between the communities of Bowie and San Simon. The system 

has been designed to focus on dual challenges:

1. Visibility hazards caused by blowing dust on a sixty mile segment of I-10 between 

Bowie and the New Mexico Stateline.

2. Unexpected snow and ice in the Texas Canyon area of I-10.

The DUST Warning System provides an early warning and detection for icy conditions in Texas 

Canyon as well as wind borne dust along I-10 using several Environmental Sensor Stations 

(ESS) and a comprehensive sensor array. Each ESS site is equipped with a snapshot Closed 

Caption Television (CCTV) camera to visually confirm any potential low visibility conditions.

System Components: The enabling technologies 

that are integrated to form the DUST Warning 

System include:

• Wireless Ethernet Networks - Based on the 

WIMAX IEEE 802.16 standard, the wireless 

network solution is integrated to serve as a 

cost-effective and reliable long-range 

communications backbone for the DUST 

Warning System.

• Photovoltaic Cells - Power for the remote 

telemetry sites are derived from renewable 

solar energy generated using photovoltaic 

cells. Initially developed to power satellites, 

the technology has gained recent 

widespread acceptance for solar powered 

remote telemetry and warning applications.

• Anemometers - These devices measure 

wind speed to predict the potential for onset of high wind conditions, which may lead 

to reduced visibility conditions.

• Forward Scatter Visibility Sensors 

Technology - It uses the forward scatter 

principle of light in the presence of 

atmospheric particles to measure the 

extinction coefficient and visibility. A highintensity infrared Light Emitting Diode (LED)

transmitter is used to illuminate the sensor’s 

Figure AZ-1. Visibility sensor in

ADOT DUST warning system.
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scatter volume. This results in a high signal-to-noise ratio and reduces the effects of 

background light variations. Visibility measurements are possible over a standard range 

up to more than 10 miles as depicted in Figure AZ-1.

• Light Emitting Diodes - LEDs have been in use as indicators for decades. As the 

reliability, heat tolerance, brightness and efficiency have increased, LED technology has 

gained widespread acceptance for application as traffic signal or warning beacon 

indications.

• CCTV Camera – Each ESS site is equipped with a snapshot CCTV Camera to visually 

confirm any potential low visibility conditions.

System Operations: The overall concept of operations for the DUST warning system is quite

simple. Sensors are used to detect high winds and low visibility conditions. In addition, CCTV 

cameras will be providing snapshots for visual confirmation of low visibility conditions, so that 

ADOT and Department of Public Safety (DPS) can make informed decisions regarding roadway 

closures and detours as needed.

The DUST warning will use Programmable Logic Controllers (PLC) to trigger various warning 

devices when wind speed thresholds are exceeded or when sensors detect that minimum 

visibility thresholds are not met at any of the monitored sites. The components of the warning 

system include:

• The DUST Warning System hardware is 

connected to the nearby ADOT Dynamic 

Message Signs (DMS) and is able to post 

messages from a set of stored DMS 

messages based on sensor inputs, as seen in 

Figure AZ-2.

• The DUST Warning System will enable 

Highway Advisory Radio Service (HARS) and 

play from a set of up to eight locally stored 

messages, based on sensor inputs.

• The DUST Warning System is capable of 

sending sensor alerts to a group of 

programmable e-mail addresses to alert 

highway operations and law enforcement staff 

of high wind and/or low visibility conditions.

Transportation Outcome(s): ADOT has implemented the DUST warning system in an effort to 

reduce the number of crashes on I-10 caused by the limited visibility experienced during certain 

weather conditions. Instrumentation detects adverse weather conditions and then alerts 

travelers of high winds and limited visibility. Additionally, the system notifies ADOT operations 

personnel of these conditions and records certain parameters for future review. Video 

equipment also assists ADOT personnel to quickly assess field conditions remotely. Although 

there are additional components located at the Texas Canyon Mountain pass, further west 

between Benson and Wilcox, that system monitors for snow and ice conditions, but does not 

trigger any public alerts. 

Under certain conditions, alert and informational messages are automatically delivered to the 

public through a variety of field components. Messages are pre-scripted and vary with 

instrumentation input. The combination of static and dynamic signing plus the HARS 

broadcasts present drivers with immediately important and usable information when needed in 

order to help prevent driver distraction and information overload. 

Figure AZ-2. Dynamic message 

sign with warning message.
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Operational personnel can access data and live video feeds plus receive email notifications. 

This allows the quick assessment, confirmation, and subsequent sharing of information with law 

enforcement and New Mexico DOT counterparts. Decisions regarding highway closures and 

remote traveler notification are expedited and more reliable. 

Implementation Issues: ADOT’s DUST warning system is not a new technology, but rather a 

second-generation prototype which expands the capabilities of an older, smaller system. There 

are issues which should be addressed as the technology evolves and consideration given to 

deploying similar systems elsewhere. Although not mutually exclusive, these issues can be 

segregated into administrative and technical areas in nature.

The administrative issues highlighted here could be considered typical in any weather-warning

project:

• The Department must commit operating and maintenance funds to sustaining the 

system, not just the initial cost for installation. Training on how to operate and maintain 

the system must be reflected in the funding allocated. 

• The integration of other measures and stakeholders, and the degree of integration, must 

be considered. For example, allowing New Mexico DOT to view Arizona weather data is 

fairly simple via the Internet. However, ensuring than an appropriate and coordinated 

multi-agency, multi-state response is provided for a large-scale, sustained weather event 

takes a substantial amount of effort. 

Technical issues discovered so far (and others will surely manifest themselves over time) 

include the following: 

• Specifying, procuring, and installing the system requires a team with specialized 

experience. Using a qualified consultant greatly helps. A warranty period should be 

included in any agreement as well as training and field shadowing to facilitate the 

knowledge transfer from the vendor to public sector Department personnel. Vendor 

technical support should include both hardware and software.

• Determining what data to collect, how to store it, review it, and how long to keep it is 

quite a significant effort. There has been some discussion that none of the data should 

be recorded due to potential liability concerns; however, that issue has not been fully 

resolved within ADOT.

• The initial calibration and set points for parameters takes time to discern. There may be 

some variability in wind speed versus soil type versus dryness, etc., that can make each 

site unique from other locations. There is a growing body of knowledge, but in the end 

the operator will need to adjust the system sensitivity until false alarms are minimized 

and the alerts delivered to the public are accurate (so dust storm messages are not 

displayed during a calm day and vice versa).

• The HARS does have serious limitations due to Federal Communications Commission 

transmission power and frequency assignment restrictions. Although the immediate 

vicinity may be covered, the signal becomes essentially imperceptible in less than a 

mile’s distance. HARS is not an effective long-distance warning device; it is only good 

for delivering instructions to travelers in the immediate area. Many question its cost 

effectiveness. 

• Email overload is one of the first observations made by new users, especially before the 

system set points are dialed in to minimize false alarms. Several users first excited 

about participating in the new system chose to later unsubscribe from the email warning 
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distribution list because of the high volume of repetitive warnings. Operations personnel 

in the field typically do not have access to email, especially after hours. Typically, law 

enforcement has no interest in receiving automated email messages but rather rely on 

ADOT notification or personal field observations.

• Sensory instrumentation and subsequent alerts are just snap shots of conditions in the 

immediate vicinity within a long corridor that in reality may be experiencing a wide variety 

of conditions. It would be cost prohibitive to place a continuous array of sensors and 

warning devices along any corridor so any proposed effort should focus on segments of 

highway where weather-related problems have already been demonstrated. Because 

this segment of I-10 in southeastern Arizona had a history of crashes and a larger-thannormal number of fatalities due to weather-caused visibility problems, it was deemed an 

appropriate location for deployment of this technology. 

• ADOT has struggled whether to periodically review weather, crash, and system 

performance data with the goal of validating whether the system is worth the cost. It is 

noted that both weather events and crashes are highly random in nature and it can be 

expected to take several years for enough data to be collected to make a meaningful 

assessment. However, ADOT knows that a single fatality has both a very high 

emotional as well as financial cost to society. If the Department can reduce the number 

of crashes then the system cost could be justified in a traditional business sense. It may 

be difficult to analytically demonstrate a reduction in crashes attributed to this warning 

system. Nevertheless, system reliability will always be an issue and maintenance 

programs have real costs that need to be justified so this particular question remains 

open. 

• All involved would do well to remember that a certain portion of the traveling public will 

either be confused by the warning messages or choose to ignore them and attempt to 

pass through an area experiencing bad weather while hoping for the best. Current 

technology will not resolve that challenge. 

Contact(s):

• Reza Karimvand, Arizona DOT, Assistant State Engineer, Transportation Technology 

Manager, 602-712-7640, RKarimvand@azdot.gov

• Farzana Yasmin, Arizona DOT, Development Team Manager, 602-712-8328

• Bill Harmon, Arizona DOT, Safford District Engineer, 928-432-4919, 

bharmon@azdot.gov

• Jon Lovell, Arizona DOT, Transportation Engineering Specialist, 602-712-7754.

Reference(s):

• Systems Engineering Analysis (SEA) for the Rural Safety Innovation Program I-10.

• Severe Weather Warning System Dual Use Safety Technology (DUST) Warning 

System.

Keywords: Visibility, Snow, Forward Scatter Visibility Sensor, Anemometer, Wind, Dust, CCTV, 

Dynamic Message Sign, Highway Advisory Radio Service
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California DOT Fog Detection and Warning System

California’s Great Central Valley suffers from Tule fog. It is a thick ground fog which reduces 

visibility to one hundred feet or less that settles in the San Joaquin Valley and Sacramento 

Valley areas of California's Great Central Valley. Tule fog forms during the late autumn and 

winter (California's rainy season) after the first significant rainfall. This phenomenon is named 

after the tule grass wetlands (Tulare’s) of the Central Valley. Accidents caused by the tule fog 

are the leading cause of weather-related traffic accidents in California.

In response the California Department of Transportation (Caltrans) contracted ICx 

Transportation to build and integrate a fog detection and warning system along a 13-mile 

section of the California Highway 99 corridor in the central part of the state. The system was 

completed in 2009.

California’s Central Valley—extending from Bakersfield in the south to Redding in the north—is 

one of the country’s largest agricultural regions. It is also a major transportation corridor, with 

Interstate 5 and California Highway 99 (CA-99) running through the valley. CA-99 in Fresno in 

the project area carries more than 100,000 vehicles per day. The region is subject to a 

particularly dense kind of fog, known as Tule fog, during the winter. In fog season, which runs 

roughly from November 1 to March 31, Tule fog can form overnight and reduce visibility to less 

than an eighth of a mile, and in some cases to nearly zero. Drivers along the corridor routinely 

would continue to drive at unsafe speeds despite the low visibility, which has led to large, 

multiple-car crashes. In November 2007, Tule fog caused a 108-car pile-up. There were two 

deaths and nearly forty injuries. The pile-up, which included 18 semi-trailer trucks, extended for 

nearly a mile and closed CA-99 for over twelve hours. The last vehicle collided ten minutes after 

the initial crash.

In addition to the threat to life and property, these major pile-ups have an enormous effect on 

the economy of the Central Valley. In order to reduce the likelihood of future multi-vehicle 

crashes, District 6 of the Caltrans is implementing a pilot project to automatically detect fog and 

warn motorists of hazardous conditions. Construction on the Fog Detection and Warning 

System (FDWS) began in October 2008.

Phase 1 was completed in February 2009 and Phase 2 was completed before the beginning of 

the 2009–2010 fog season on November 1, 2009. The project covers a thirteen-mile stretch of 

CA-99 south of Fresno, California.

System Components: The FDWS system consists of visibility 

sensors, speed detectors and cameras to detect congestion and 

visibility problems that could affect driver and passenger safety.

The installation is forty percent solar powered and uses both 

point-to-point and point-to-multipoint wireless radios to provide 

network connectivity. Local field controllers allow the field 

equipment to work autonomously if there is a break in 

communications to the central system. 

System Operations: Through intelligence built into the ICx 

CameleonTM ITS product, the system alerts motorists 

automatically of dangerous weather conditions and slow speeds 

by using changeable message signs (CMS) and highway Figure CA-1. Sensor array.
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advisory radio (HAR). The system will soon be incorporated into a 511 traffic web page and 

telephone system.

Speed detectors have been deployed every quarter of a mile, and fog sensors and CMSs 

deployed every half mile. Using the data collected from the sensors, the CMSs warn drivers of 

the presence of fog downstream and instruct them to slow down when they are in dense fog. 

When slower speeds are detected downstream, the CMSs warn drivers of the slower traffic 

ahead. HARs, roadside weather stations, cameras and multi-color changeable message signs 

are included.

The FDWS will use sensors to detect both visibility and speed on CA-99 in the project area. To 

measure visibility, the team selected the PWD10 forward scatter sensor developed by Vaisala. 

The sensors have been installed every half-mile covering both directions of the freeway. They 

are installed at driver eye level to ensure the system is reporting the current conditions as seen 

by the driver. In addition, the project team has installed SmartSensor HD radar spot speed 

sensors from Wavetronix every quarter-mile through the project area. These radars are capable 

of measuring traffic volume, classification, speed, lane occupancy and presence in both 

directions of travel. Figure 1 shows the sensors on the roadside. These two sensing 

technologies combine to provide a more complete picture of traffic and visibility conditions than 

has ever been attempted on a large scale. 

The data from the sensors will be used to assess both visibility conditions and, equally 

importantly from the perspective of both travelers and traffic managers, speed differential at 

downstream locations on the freeway.

Due to the relatively rural nature of the project area, dedicated wire line communications are not 

available. Moreover, even if they were, the cost of trenching to connect into such systems would 

be prohibitive. As a result, all system communications are wireless. The communications 

system uses Proxim wireless devices to communicate between devices in the corridor. 

Backhaul communications to Caltrans’ Transportation Management Center (TMC) is done using 

Verizon Wireless EVDO modems. Also due to the scarcity of fixed infrastructure, forty percent of 

the field equipment runs on solar power. 

Data processing ensures that the data collected in the field is available in a useful format to 

travelers and to traffic managers. The system was developed with two levels of data processing.

Under normal system operations, all data are collected in the field and transmitted wirelessly to 

the TMC. There it is processed using the CameleonTM ITS platform developed by ICx 360 

Surveillance. If there are significant speed differentials on the freeway or if there is fog, 

Cameleon automatically generates messages for the data dissemination systems. If an incident 

has occurred, the CMS’s will warn drivers of slower traffic ahead in order to prevent chainreaction collisions.

Planned enhancements include providing the speed and visibility data from the system to the 

new 511 traveler information system for the southern Central Valley. The 511 system will inform 

travelers of problems in the project area via the telephone and the Internet before they reach it, 

possibly before they even leave their home or office. This will help reduce the impact of severe 

fog by minimizing the number of vehicles on the roadway.

As the system is further refined and enhanced, Caltrans envisions that it will have some or all of 

the following features:

• Full Matrix Color CMS to provide better information
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• Road Weather Information Systems (RWIS) at various locations to monitor the full range 

of weather conditions, including rain, wind, humidity and temperature. The data from 

these sensors could potentially be used to predict fog.

• HAR reports, with alerts to travelers using extinguishable message signs

• Closed Circuit Television Cameras to provide more detailed information to the TMC and 

to the public over the Internet

• Pulsing in-pavement lighting to be used to slow traffic down under certain conditions 

(such as when there is an incident ahead) The lights would not be used during low 

visibility until an incident has occurred for fear the lights would guide drivers to move at 

unsafe speeds.

• Thermal Cameras

• Incident detection using advanced radar detection

Transportation Outcome(s): The system alerts motorists automatically of dangerous weather 

conditions and slow speeds by using CMS’s and HAR. When slower speeds are detected 

downstream, the CMS’s warn drivers of the slower traffic ahead. If an incident has occurred, 

the CMS’s will warn drivers of slower traffic ahead in order to prevent chain-reaction collisions. 

Presently, the system only employs CMS’s and HAR to communicate road conditions t0 

travelers. Both of these methods are very effective. The addition of the 511 system addresses 

the shift to mobile data devices and the increased reliance by the motorist on receiving this 

information while traveling. Once the fog detection data is integrated with the 511 system, it will 

help reduce the impact of severe fog by minimizing the number of vehicles on the roadway.

Implementation Issues: The FDWS installation involved a very short design-build cycle and 

innovative uses of existing technology. A number of issues were encountered in the 

implementation of the FDWS:

• Internal controls needed to be reconciled with the aggressive schedule and cost 

constraints of the FDWS.

• Existing infrastructure had to be reconfigured in order to merge the old and new 

components into a unified system, under the control of the Cameleon software.

• Evaluations of new technologies, such as Color CMS’s, took time and resources to 

complete.

• User interfaces to the TMC needed to be developed around existing procedures, policies 

and systems.

• Caltrans policies regarding information technology security issues needed to be 

addressed due to the nature of the communication systems deployed by the FDWS.

Additionally, the density of detectors was limited by funding. In general, more detection 

capability equates with a more robust coverage of fog events. However, the nature of the 

funding for this project, did not allow for even small deviations from the allotted and agreed upon 

budget. Finally, there were concerns regarding the aesthetics of the project, due to the 

perceived clutter that the number of proposed field elements would present to the motorist.

Contact(s): 

• John Liu, California Department of Transportation District 6, 559-488-4082, 

john_liu@dot.ca.gov

• Peter Dwyer, ICXT, peter.dwyer@icxt.com

• Liz Justison, ICXT, liz.justison@icxt.com
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• Chris D’Agosto, ICXT, chris.dagosto@icxt.com

• Fred Vey, ICXT, fred.vey@icxt.com

• Michael Berman, ICXT, michael.berman@icxt.com

Reference(s):

• Fresno Fog Detection and Warning System <http://gs.flir.com/uploads/file/casestudies/case-study_caltrans-fog.pdf>

Keywords: Fog, Weather, ATMS, Warning System, Detection, Speed, Visibility, Wireless, Solar 

Power.
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California DOT Icy Curve Warning System

Fredonyer Pass, located in northeastern California, is a five-mile segment of State Highway 36 

in Lassen County that has a history as a high-collision location, including multiple fatal crashes 

involving local residents. The vast majority of these crashes (note in this document, the terms 

crash and collision may be used interchangeably) occurred when the pavement was icy, despite 

static signage that the California Department of Transportation (Caltrans) had installed to 

increase motorist awareness.

To address this, Caltrans deployed a system consisting of pavement sensors to detect icy 

conditions, in combination with dynamically activated signage to provide motorists with real-time 

warning when icy conditions are either imminent or present. The intention of the system was to 

use real-time messaging to increase motorist vigilance and reduce the number of crashes 

occurring during icy pavement conditions. The system consists of pavement sensors to detect 

icy conditions, in combination with dynamically activated signage to provide motorists with realtime warning when icy conditions are either imminent or present. It alerts motorists of icy 

conditions, eliciting a decrease in vehicle speeds during such conditions. Consequently, lower 

vehicle speeds are expected to translate to reduced crashes along the length of the curves 

which have presented safety challenges in the past. 

System Components: Each system consists of a Road Weather Information System (RWIS) 

with roadway sensors and two Extinguishable Message 

Signs (EMS) with flashing beacons. Specialized scripts 

are executed in the RWIS Remote Processing Unit (RPU) 

that evaluate the status of the roadway sensors and 

determine when the ice warning should be active. A signal 

from the RPU then turns on the warning signs. At the 

summit system, a Closed Circuit Television (CCTV) 

camera is also present to allow the TMC in Redding to 

monitor conditions at the pass.

System Operations: This system is collectively known as 

the Fredonyer Pass Icy Curve Warning System (ICWS). It 

is comprised of two similar but separate warning systems: 

Fredonyer Summit ICWS and Fredonyer East ICWS. The 

technologies employed in each system include a RWIS, 

which continuously monitors the road surface condition 

and identifies when icy or packed snow conditions are 

present; and two EMS, which provide dynamic warnings to 

motorists when icy or packed snow conditions are present. 

One RWIS is placed in the heart of each curve at a location 

determined by to experience icing conditions most 

frequently. One EMS was placed on the approaches to each curve at a location to provide 

adequate braking distance for vehicles headed into an icy curve. 

A schematic showing the location of the Intelligent Transportation Systems (ITS) elements of 

the system is presented in Figure CA-3. 

Figure CA-2. Road weather 

information system at 

Fredonyer East ICWSs.
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Figure CA-3. Schematic of Fredonyer Pass and Icy Curve Warning System.

The original, vendor-supplied system components were installed during the summer of 2002, 

including RWIS pavement sensors, RWIS towers, solar panels, and EMS. Over time however, it 

became evident that this system would not reliably operate in the manner envisioned by 

Caltrans. Instead, the system was rebuilt by Caltrans District 2 ITS Engineering and highway 

maintenance personnel. Ice detection optimization continued for about two seasons after the 

hardware was corrected.

Transportation Outcome(s): In order to determine the safety effects of the ICWS, an 

observational before-after study using the Empirical Bayes technique was employed. This 

evaluation determined the effect of ICWS on crash frequencies. The results found that the 

deployment of the ICWS reduced the number of annual crashes by 18%. As no other changes 

occurred along the study segment (additional safety improvements, geometric changes, etc.), it 

is reasonable to attribute this observed safety improvement to the ICWS. Additionally, a crash 

rate method was used to investigate the effect of the ICWS on crash severities, with a focus on 

ice-related accidents. The results indicated that the ICWS has reduced crash severities. As an 

outcome of reduced crash severities, the system was estimated to provide safety benefits of 

$1.7 million dollars per winter season during the after deployment study period (2008-2009, on 

account of time lag in crash data availability). Given that 1.5 years of after-period data was 

available for analysis, it would be advisable to revisit the safety performance of the Fredonyer 

ICWS at some point in the future when more years of crash data are available. Overall however, 

the initial safety evaluation results indicate that the system is having a positive impact on 

reducing crashes. 

From the perspective of winter maintenance personnel, the ICWS is an improvement over 

typical static metal signage. Observations made over time have indicated that as the winter 

progresses, the system works better. The use of additional pavement sensors for detection of 

conditions in multiple lanes could improve system accuracy and reliability. The data produced 

by the ICWS is not presently employed by maintenance forces for any activity, although the 

CCTV camera associated with the system’s RWIS at the summit is used frequently to obtain 

visual information on present conditions. 

The ICWS’s in District 2 are the only focused pavement section ice detection and warning 

systems that have been successfully deployed and function properly. While the results are 

preliminary while data collection is ongoing, there may be a real and significant safety 

improvement and improvement in driver behavior due to the systems’ presence. Traditionally, 
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these types of problem areas required an expensive roadway realignment to solve reoccurring 

icing. Deployment of ICWS systems may allow for an interim, lower cost option that provides a 

safety benefit until funds for a full realignment can be secured.

Implementation Issues: The ICWS was not considered fully operational and reliable until the 

winter season of 2008-2009. Following, an evaluation of the performance of the ICWS focusing 

on the metrics of speed reduction under various conditions and safety performance through 

crash reduction was conducted. The results of the statistical analysis of speed data suggest that 

the system is working as intended and that vehicle speeds are significantly lower. As one would 

expect, mean speeds were lower when the system was turned on versus off as well as during 

the day and at night. When general wet weather (snow, rain, etc.) conditions were evaluated, it 

was found that mean speeds were reduced when the system was on versus off during both the 

day and at night. The real effectiveness of the Fredonyer ICWS on vehicle speeds is its impact 

during clear, cold and not dry conditions, when snow melting or general water/ice pooling from 

the wet and cold environment of the curve locations may produce runoff across the roadway in 

the target curve and result in ice formation. Mean speed differences exceeding 3 mph were 

observed during such conditions during both the day and at night at a majority of sites. 

However, only a limited number of mean speed differences were found to be greater than 5 

mph. As the speed readings employed in this evaluation were collected at sign locations in 

advance of the curves of interest/concern targeted by the ICWS, it is possible that the observed 

changes in mean speeds reported here are translating into even more significant reductions by 

motorists as they enter and traverse each curve. When examining different levels of manned 

chain control versus the system state and time of day, it appears that the greatest impact of the 

ICWS is when R-1 control is in effect. (R-1 control is a requirement for chains on tires of 

commercial vehicles, and snow tread tires or chains on all other vehicles.)

Feedback by Intelligent Transportation Systems (ITS) engineering indicated that following the 

rebuilding of the ICWS, it is generally functioning as expected. However, observations over 

several years of operation have indicated that the system has difficulty identifying road 

conditions during the early winter. The use of additional sensors in such cases would address 

this issue. Also, employing data from supplemental sensors (such as air temperature, 

precipitation, et cetera.) could possibly allow the system to compensate for times that roadway 

surface temperature and condition data is not sufficient in identifying potential icing conditions. 

When considering similar systems for deployment elsewhere, it is especially important to select 

roadway sensors that can be tested and calibrated easily, and to employ data collection 

equipment in the system that uses open and easily programmed software. 

Finally, feedback provided by the California Highway Patrol (CHP) indicated that drivers appear 

to be slowing down when the ICWS is on (particularly in vicinity of the targeted curves). This is 

only perception though, and there has been no analysis performed by CHP (on ticket records, 

for example) to verify whether it is in fact the case. It was also believed that crashes over the 

pass have dropped in recent years although, again, no analysis of data has been performed to 

confirm this view. The thoughts of CHP on this drop were that it could be related to the ICWS, 

as well as manned chain control policies employed by Caltrans. In general, the system appears 

to be accurate in indicating ice conditions.
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Contact(s): 

• For system information:

Ian Turnbull, P.E., Chief, Office of ITS Engineering and Support, Caltrans, District 2, 

1657 Riverside Drive, M/S 14, Redding, California 96001, ian_turnbull@dot.ca.gov

• For evaluation information:

David Veneziano, Ph.D., Research Scientist, Western Transportation Institute, Montana 

State University, PO Box 174250, Bozeman, Montana 59717-4250. 

david.veneziano@coe.montana.edu

Reference(s): 

• Rama, P., and Luoma, J., “Driver Acceptance of Weather-Controlled Road Signs and 

Displays,” Transportation Research Record 1573, Transportation Research Board, 

National Research Council, Washington [DC] (1997), pp. 72-75.

• Carson, J., and F. Mannering. The Effect of Ice Warning Signs on Ice-Accident 

Frequencies and Severities. Accident Analysis and Prevention, 33(1), 2001.

• Hauer, E. Observational Before-After Studies in Road Safety: Estimating the Effect of 

Highway and Traffic Engineering Measures on Road Safety.

• Pergamon Press/Elsevier Science Ltd, Oxford, England, 1997.

• Federal Highway Administration. Motor Vehicle Accident Costs. U.S. Department of 

Transportation, Washington, DC, October 1994.

• Bureau of Labor Statistics. CPI Inflation Calculator. Available at: 

<http://www.bls.gov/data/inflation_calculator.htm> (Accessed on March 20, 2011).

Keywords: Icy, Ice, Ice Detection, Automated Warning, Safety, Performance, Weather, Visibility, 

Wireless, Solar Power
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Colorado DOT One Pass Clearing Operations

Many agencies continue to be challenged with removing snow on an increasing number of lanes 

and shoulders with the same or fewer trucks and operators, while still needing to meet the 

public’s expectations. There is a necessity to identify how to plow wider and faster to maintain 

or increase services without adding personnel. The Colorado Department of Transportation’s 

(CDOT) original goal was to double operator production to meet the expected levels of service. 

There are two approaches tried and proven:

1. Using wider front plows to clear a 12 foot lane in one pass (see Figure CO-1) has been 

proven to reduce the number of passes (rounds) needed, has saved fuel and has 

reduced labor costs. The expected savings for average fuel costs and average labor 

costs are between 20% and 50%. The benefit to cost ratio exceeds one the first year.

2. Trailer plows, also known as Tow Plows (TP) (see Figure CO-2); have allowed one snow 

plow truck and one operator to clear widths over 24 feet at high speeds, providing a level 

of performance never before seen in the industry. Previous trucks with wing plows 

generally cleared a path of 16 feet or 

less at speeds less than 30 miles per 

hour. TPs have cleared up widths up 

to 25 feet at speeds above 50 mph in 

open, safe conditions. The benefit to 

cost ratio exceeds one when it replaces 

a second truck, and it exceeds one 

within one year to five years of 

operation.

System Components: Most transportation 

agencies use 10-foot, 11-foot, or 12-foot front 

plows. Using a 14-foot front plow allows one 

operator to clear one lane in one pass, from 

centerline stripe across either edge line stripe. 

The extra cost of 14-foot plows is miniscule 

compared to the current cost of front plows. 

TPs allow one operator to clear widths up to 25

feet, with the ability to vary the clearing path 

from 11 feet to 25 feet with a simple control in 

the cab. The TP hooks and tows behind a 

snow plow truck. In operation, it can be 

steered into the adjacent lane, clearing and 

treating an additional lane in the same pass. 

The TP can be steered around parked cars as 

needed. The cost of a TP is less than the cost 

of a conventional snow plow truck.

System Operations: A front 14-foot plow, when 

properly designed, can vary its clearing path 

from 11.5 feet at 35 degrees to 12.5 feet at 25 

degrees, by using the original control sticks in 

Figure CO-1.

Truck with 14 ft. wide front plow.

Figure CO-2. Tow plow being loaded with 

salt.
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the cab for other front plows. The former plow position can provide fuel savings due to its acute 

angle and the latter can clear a 12-foot lane in one pass. It hooks to the trucks just like other 

front plows.

A TP hooks to a snow plow truck like any trailer with air brakes and it needs controls to deploy. 

Agencies have used the existing hydraulic controls on wing plow trucks to deploy TPs. One can 

divert the hydraulics used for existing wing plows to provide steering and moldboard lift. 

Another option is to add two hydraulic valves and duplicate the front plow control stick. With this 

option, one stick deploys and retrieves the TP. 

TPs with spreaders require additional hydraulic circuits for spreader and fan controls. Some 

TPs are self-sufficient by having on-board diesel power and hydraulics. Such TP units can be 

used as brine trailers for anti-icing practices while in tow before a snow storm, or during the 

storm while deployed.

Transportation Outcome(s): Wider front plows provide tremendous advantages on interstates 

and expressways because they clear an entire 12-foot lane, thereby eliminating the need for a 

second round and reducing the exposure time and frequency of exposure between snow plow 

trucks and traffic. 

The practice can also clear both the center line stripe and either the left or right edge line stripes 

when clearing the 12-foot lane in one pass resulting in exposed stripe markings earlier in the 

snow storm. 

A third advantage is that the practice discharges the windrow beyond the edge lines, positioning 

it such that it is more difficult for traffic to suck the windrow back onto the pavement between 

cycles of plowing. In general, two lane collector roads (with and without shoulders) and rural 

interstates can benefit by clearing the entire lane in one pass.

There has been some indication that eliminating the second plowing round on collector roads 

(which have adjacent ditches and no shoulders) may eliminate snow plow truck accidents by 

allowing the operator to discontinue crowding the edge of pavement on the second round. 

Further, when the operator does not make the second round, he cannot plow off the first pass 

chemical treatment, thereby eliminating the need to apply a second application of chemicals.

TP trucks can do the work of two snow plow trucks. One such manifestation of this capability is 

clearing the truck climbing lanes on the first round, and thus immediately returning the climbing 

lane to service instead of waiting until the second round. Similarly, TPs can benefit routes with 

reverse passing lanes where snow plow trucks need to clear two lanes for a few miles and then 

only one lane (and shoulder) for several miles, repeating this alternating passing opportunity for 

many miles. Therefore, passing opportunities are provided immediately after the first round.

Implementation Issues: 

• Many state transportation agencies have assumed that 14-foot front plows cannot 

operate on highways. However, the Missouri Department of Transportation now has 

over 500 plows operating on interstates, expressways, urban multilane signalized areas 

and collector roads with 10-foot, 11-foot, and 12-foot lanes with and without shoulders.

• Accessibility to maintenance shops for parking and blade-changing may be an issue; 

however, the 14-foot plows are designed to pivot farther and the moldboards are clipped 

to allow entry into buildings.
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• These plows must be used on an appropriately sized truck. The 14-foot plows were first 

implemented on ten-wheelers but are now used and proven on six-wheelers with gross 

vehicle weight ratings of 26,000 lbs. or more. These plows are not to be used on lighter 

trucks. Most trucks have 12,000 lb. front axles or heavier.

• There may be some concern with the operating width of the 14-foot plows. Plow 

designs cause the clearing path to always favor the discharge side. Thus, the leading 

edge is no closer to center line than conventional 11-foot and 12-foot plows. 

Additionally, the truck mirrors are at least nine feet wide on most trucks. Therefore the 

front plow is only just outside of the mirrors. Finally, an important benefit of this plow is 

that it allows the operator to reach the edge of pavement without crowding the steer tire 

to the edge of pavement.

There are several implementation concerns with the TP, such as the following:

• “Too large to operate on our highways!” Very few could believe that one could plow two 

lanes wide with one truck and do it safely. TPs have proven to be safer for gang plowing 

by eliminating many of the gaps between existing trucks. Brine tanks or spreaders have 

provided conspicuity for rear recognition to avoid rear end accidents.

• “Our snow plow trucks do not have enough horsepower to pull.” TPs operate at extreme 

angles from 60 to 90 degrees compared to front plows which operate at 30 degrees from 

the rear. This acute angle provides better casting to move snow with less horsepower. 

• “It costs too much.” A TP costs ten times as much as a front plow, but it replaces a 

second truck and operator.

• “Our wing plows are being hit from the rear so the TP, being larger, would create more 

accidents”. All TPs are required to have brine or material spreaders lending conspicuity 

to the rear. Practice has proven that TPs do not get hit like wing plows.

• “The TP will not handle our deep snow storms.” Videos of operations in Maine, Canada,

and in areas of Ohio with lake effect show that Tow Plows can handle deep snow quite 

well.

• “We cannot use a TP truck blocking traffic on a two-lane rural interstate highway.” This 

had been a major concern, but with field experience it is being overcome. In some 

cases the use of TPs is preferred and endorsed by the state highway patrol. Seek more 

information on this issue from the contacts listed below; specifically, Robert G. Lannert 

can provide current information and states’ practices.

For cautionary purposes, it should be noted that snow plow trucks should always operate at 

safe speeds for the conditions. Operators should always follow agency protocol and 

procedures. Operating speeds must consider the equipment design, potential obstacles, the 

road condition (rutting, potholes, friction, and operating environment), and the operator’s training 

and abilities. There are major differences in front plow, wing plow, and underbody plow designs 

where some may not safely operate at speeds above 20 mph to 40 mph, much less than rural 

interstate speeds. However, plowing faster can reduce or eliminate rear end accidents with 

snow plow trucks.

Contacts: 

• Robert (Bob) G. Lannert, Retired MoDOT Engineer, Maintenance Operations, (Mr. 

Lannert’s current telephone number can be obtained via a request through email to 

MoSnowKing@aol.com). 

• Tim Chojnacki, MoDOT Maintenance Operations, E-mail Mr. Chojnacki at

Tim.Chojnacki@modot.mo.gov for current telephone number and information about 

MoDOT’s experience with more than five 14-foot plows and more than 70 TPs.
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• Phil Anderle. Contact Mr. Anderle at 970-350-2100 or Phillip.Anderle@DOT.State.Co.Us

for questions about Speed Management on Colorado I-70 and other routes using Patrol 

cars and snow plow trucks to maintain safe travel speeds and provide continuous flow of 

traffic during inclement weather conditions.

Reference(s): 

• AASHTO Technical Technology Implementation Group, TowPlow

<http://tig.transportation.org/Pages/TowPlow.aspx>

• Snow King Technologies - Current lists are maintained for Tow Plow reports, pictures, 

videos, and user lists: <http://www.TowPlow.com>

• Ohio DOT TowPlow Report, May, 2011 

<http://www.towplow.com/resources/Ohio+TowPLow+report+.pdf>

• Maine DOT Research Division, Technical Brief(10-4), Second Year Evaluation of the 

Viking-Cives Tow Plow, June 2010.

<http://www.maine.gov/mdot/tr/documents/pdf/report1004final.pdf>

• Missouri Governor’s Award for Productivity and Innovation in State Government 2007, 

October 2007. "Fewer Fatalities, TowPlow Invention Recognized." 

<http://www.modot.org/newsandinfo/District0News.shtml?action=displaySSI&newsId=13

566>

• TRB Publication Snow08-003, 2008. "Plowing Wider and Faster on 21st-Century 

Highways by Using 14-ft Front Plows and Trailer Plows Effectively." Pages 261-266 

<http://pubsindex.trb.org/view.aspx?id=863382>

Keywords: One pass clearing, 14’ snow plow, trailer plow, tow plow, high speed plowing.
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Colorado DOT Variable Speed Management System

Colorado State Highway 82, in Snowmass Canyon (between Aspen, CO and Glenwood 

Springs, CO) is composed of an elevated southbound roadway that shades the northbound 

roadway during certain times of the day causing rapidly changing freezing conditions. The 

Colorado Department of Transportation (CDOT) installed the Variable Speed Management 

System which consists of a complete Road Weather Information System (RWIS), using newly 

developed non-intrusive pavement weather sensor technology. The pavement sensors monitor 

traction/friction conditions in the area that is shaded, and allow for alerts when conditions 

warrant. The system is capable of monitoring wet conditions, wet conditions with traction loss 

as freezing begins, and snow and ice conditions. The system wirelessly communicates to a 

single variable message sign (VMS) and a single variable speed sign (VSS) that are located 

nearly a mile in advance of this northbound section of highway in Snowmass Canyon (see 

Figures CO-3 and CO-4).

System Components: The system consists of the following major components:

• Variable Message Sign

• Road Weather Information System (RWIS), which consists of the following:

o Remote Processor Unit

o Non-Intrusive Surface State Sensor

o Non-Intrusive Surface Temperature Sensor

o Air Temperature/Relative Humidity Sensor

o Precipitation Identifier and Visibility Sensor

o Ultrasonic Wind Sensor

o Pan-Tilt-Zoom Color Camera

o Relay Device Control

o Wireless Device Control

Figure CO-3. RWIS 

Snowmass Canyon.

Figure CO-4. Alert of wet roads.
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System Operations: The system provides continuous monitoring of atmospheric and pavement 

weather conditions to determine changing driving conditions that will impact the motorist and 

alert transportation managers of these changing conditions. The Non-Invasive pavement 

weather sensors are capable of monitoring changing traction values that will impact driving 

conditions for the motorist. They are also capable of alerting the motorist of these conditions by 

displaying messages on the variable message sign and potentially providing advisory speed 

limits as a result of these changing pavement conditions.

The system monitors current atmospheric conditions by monitoring when precipitation is 

occurring in the form of rain, freezing rain, or snow, with the ability to display rates and 

accumulations. The system is able to provide alerts to Colorado Department of Transportation 

(CDOT) operations of these changing atmospheric and pavement weather conditions allowing 

for remote access to conditions by computer and cell phone. The camera allows for live images 

of changing weather conditions at the site.

The system monitors traction level thresholds. When slippery thresholds for wet and icy 

thresholds are reached, activation of different messages such as “Wet Roads Ahead” or “Icy 

Roads Ahead” are produced by the RWIS processor. The “wireless device control”, utilizing 

spread spectrum radios, activates these different messages in the VMS that is located nearly a 

mile in advance of this stretch of highway. The “wireless device control” also is capable of 

providing different controls for different suggested speeds with the “variable speed sign”. 

Transportation Outcome(s): The unique road topography of Colorado State Highway 82 caused 

shading and precipitation build-up on certain portions of the road at various times of the day, 

resulting in a large number of winter weather related accidents during the several years prior to 

the installation of this Intelligent Transportation System. The first winter of operation resulted in 

no winter weather related accidents in this section of highway in Snowmass Canyon.

Implementation Issues: Buried telephone was not readily available at the RWIS and VMS sites 

so a wireless cell phone modem was installed at the RWIS site to communicate to the RWIS 

site. Communication was also established from the RWIS site to the VMS site using a spread 

spectrum radio system as described previously. Even if there is a cell phone outage the RWIS 

can communicate to the VMS site. 

The Variable Speed Limit Sign which was installed and operated with no issues, but was later 

removed at the request of CDOT Staff Traffic.

Contact(s): 

Mike Curtis, CDOT Region Traffic Engineer, 970-683-6277, Michael.Curtis@dot.state.co.us

Reference(s):

• Jerry R. Waldman, Vaisala, Inc. jerry.waldman@vaisala.com

• Gary Eckley, Sturgeon Electric, geckley@myrgroup.com

• Fred Ingham, Skyline Products, Inc., FredIngham@SkylineProducts.com

Keywords: Intelligent Transportation System, atmospheric weather sensors, non-invasive 

pavement weather sensors, hazardous atmospheric weather, road weather traction conditions, 

and alert motorists alerts, variable message signs, variable speed signs
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Florida DOT Bridge Wind Speed Alerting System

The Florida Department of Transportation (FDOT) has deployed a high-wind alert system for 

road bridges. The system assists the transportation and public-safety communities by providing 

real-time wind speed status information during severe weather events from each monitored 

bridge structure. This information is used to assist transportation managers with bridge closure 

decisions. 

Historically in Florida when a severe weather event occurs, such as a tropical storm, hurricane, 

or nor’easter, local law enforcement personnel must deploy to each bridge in advance of the 

weather event. The officer takes periodic wind speed measurements and reports the information 

to their local law enforcement agency which may eventually make the decision to close a bridge. 

This protocol puts law enforcement personnel in harm’s way unnecessarily and deploys them 

inefficiently precisely during a time when they may be needed elsewhere. Further, requiring 

them to make wind speed measurements with hand-held anemometers is not an accurate 

means of collecting meteorological data. There is also minimal dissemination of the pertinent 

wind speed data to local and regional public safety and transportation stakeholders with this 

protocol.

With the new FDOT wind alert system, these shortcomings will be addressed. The data is 

reliably collected from the system, and it is automatically and instantly disseminated to FDOT 

Regional Traffic Management Centers (RTMC) and to local public safety officials. All parties will 

have more accurate data from which to make informed decisions about critical issues like bridge 

closures and evacuation routes.

The system has been deployed on over twenty bridges in northeast Florida as part of a pilot 

project. All critical waterway bridges and interchange flyovers in this area of the state were 

instrumented. This included all barrier island bridges, most river bridges and the three major 

highway interchanges in the Jacksonville, FL area.

The reduced expenses associated with this project is due to the use of low cost wind-only 

detectors and solar-powered satellite transmitters that 

utilize a free telemetry service offered by the National 

Oceanographic and Atmospheric Administration 

(NOAA) called the Data Collection System (DCS). 

There is therefore no monthly reoccurring operational 

cost for the system (other than maintenance). The 

installation cost to instrument a bridge is approximately 

$10,000 (material and labor). FDOT is currently 

procuring satellite communications ground station 

equipment to enhance the dissemination of data to 

RTMCs state-wide.

System Components: Each bridge is outfitted with a 

Data Collection Platform (DCP) that includes an 

ultrasonic wind sensor installed at approximately ten 

feet above the bridge road deck, as shown in Figure 

FDOT-1. The wind sensor connects to a data logger 

that performs analytics to discern wind gusts and 

continuous high winds. Multiple alarm thresholds are 

Figure FL-1. FDOT bridge wind 

speed monitor installation.
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used to detect high wind conditions, triggering the data logger to transmit an alert message via a 

NOAA Geostationary Operational Environmental Satellite (GOES). The satellite transmitters 

are solar powered. The GOES transmits alerts to FDOT, where they can be disseminated via 

the FDOT statewide area network or via the Internet.

System Operations: Sampling of wind conditions is designed to maintain a low-power draw for 

the installation. Wind measurements are performed during one minute sample periods that are 

spaced ten minutes apart. Wind anomalies associated with passing vehicles are filtered out 

during this process, ensuring that only continuous winds and gusts are reported. 

If the wind conditions trigger any of the multiple alarm thresholds, one or more alert messages 

are relayed via GOES to FDOT. Currently, FDOT is building two satellite communications 

ground stations to receive bridge wind alerts from GOES. Once received, those alerts are 

disseminated to the state-wide RTMCs. The main ground station is strategically located away 

from the coastline and next to a FDOT communications network hub. FDOT operates a 

redundant statewide area network over microwave and fiber links that provides a highly reliable 

connection to the RTMCs (these connections are 99.999% reliable, experiencing just 5 minutes 

of down time per year). This feature will help ensure that data is securely and reliably 

disseminated to the RTMCs even during severe weather events that may compromise 

commercial telecommunications infrastructures. 

In the RTMCs computers will monitor the wind speed alerts and display them graphically on a 

map of the area. Alerts are received at the RTMC once wind speeds at any bridge reach thirty 

miles per hour (mph). Alerts continue to be received for each additional 5 mph incremental 

increase. The RTMC personnel can inform local public safety officials of each new alert 

condition on a bridge, giving law enforcement officers enough time to deploy and secure a 

bridge for closure. The system will also inform RTMC personnel when wind conditions are 

receding. 

An additional software tool is being developed to provide authorized local public safety and 

emergency management personnel direct access to the wind speed data. FDOT is developing 

an Internet web application that will permit local officials to monitor the FDOT wind alert data 

securely over the Internet via dissemination from the NOAA ground station in Virginia. This 

secondary means of viewing the wind alerts will give hundreds of authorized public safety 

officials the ability to monitor local bridge wind speed conditions without compromising FDOT 

internal network performance or security.

Transportation Outcome(s): This new FDOT bridge wind speed alerting system will provide a 

more efficient, safe, and accurate method for collecting and disseminating information about 

potentially dangerous wind conditions on bridges. In addition, this new system will be able to 

share severe weather data with the FHWA and its Clarus initiative, as well as other agencies 

such as the National Weather Service. 

One of the most significant benefits of this project is the low-cost way in which it was 

implemented. The use of the NOAA GOES system to collect wind speed alerts from the bridges 

will create a substantial savings on operational costs. For example, had FDOT used cellular 

telephone modems (a common approach) to communicate with the bridge DCPs, an eventual 

statewide deployment could cost the state $750,000 over five years, just for the cell phone bill. 

The use of solar panels saves even more money since running power lines to remote bridge 

locations is very expensive.
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Implementation Issues: The installation of the bridge wind speed monitors required FDOT and 

its contractors to develop a mounting method that was performed quickly to minimize lane 

closure time, but also robust enough to withstand bridge vibrations and severe wind conditions. 

The location on each bridge was usually chosen to be the highest point, but also a point with a 

clear view of the southern sky so that the satellite transmitter could communicate with GOES. 

To avoid return visits to bridges to make installation changes, each bridge DCP was configured 

and initially tested on a rooftop Florida DOT test stand before being deployed. 

Contact(s): 

•

• Randy Pierce, Florida DOT Telecommunications Administrator, 850-410-5608, 

randy.pierc@dot.state.fl.us

• Peter Vega, Florida DOT District 2 ITS Engineer, 904-360-5463, 

peter.vega@dot.state.fl.us

Reference(s): 

• Florida DOT, Sunguide Disseminator Newsletter, October 2011. “A New Public Safety 

Focus for FDOT and ITS,”

<http://www.dot.state.fl.us/trafficoperations/Newsletters/2011/2011-010-

Oct.pdf#page=5>

• NOAA Data Collection System Website <http://www.noaasis.noaa.gov/DCS/>

•

Keywords: wind, bridge, high wind warning system, public safety, emergency management, 

traffic management centers, advisory strategy, severe weather, hurricane, tropical storm, 

evacuation, high-profile vehicles, safety, satellite, NOAA, data collection system, data collection 

platform, sensor, solar-power.
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Idaho TD Winter Maintenance Performance System

The Idaho Transportation Department (ITD) is in the final stages of developing its Winter 

Maintenance Performance Measures System which will include 87 Road Weather Information 

System (RWIS) sites. At the time of publication, sixty sites are operational. Statewide 

implementation of the system began in 2011. Currently, ITD is identifying the performance 

levels of its winter maintenance operations in all districts. Depending on the results of this effort, 

some existing maintenance practices in various 

locations may be altered to increase operational 

efficiencies. ITD anticipates there will be several 

seasons of continual improvements in the RWIS 

network while allowing time for appropriate 

operational adjustments to be made.

System Components: Each RWIS site (see Figure 

ID-1 for an illustration), in addition to the atmospheric 

sensors, typically has two road surface sensors: one 

to measure the road’s grip coefficient (DSC111); and 

one to measure road surface temperatures 

(DST111). 

Additionally, ITD is developing a system to 

automatically track maintenance data. Similar to 

many states, ITD is moving toward Automatic Vehicle 

Location (AVL) and Mobile Data Collection (MDC). 

Information on salt usage, anti-skid, liquid quantity 

usage, application rates and plow down/up time is 

currently manually recorded and entered into a 

database. 

ITD plans on automatically collecting this information from its winter maintenance fleet, and 

integrating it into the state’s Maintenance Management System (MMS) database – thereby 

eliminating the human generated reports that were time consuming and error-prone. 

Having such an automated system will also allow ITD to integrate with the automated RWIS 

performance measure system for expedited data fusion, allowing rapid review, critique and 

operational adjustments to minimize deviation from the new Best Management Practices (BMP). 

System Operations: In responding to winter storms, the treatment objective is to minimize the

“ice-up” time. ITD has developed a performance measure Index. Specifically, the Performance 

Index is a measure of ice duration per unit of storm severity. Storm severity is modeled using 

an empirical formula that utilizes wind speed, surface precipitation accumulation, and surface 

temperature. Ice duration is defined as the amount of time grip falls below 0.6. Data collected 

from the RWIS stations is used to determine various parameters in the Performance Index 

formula. This metric allows for accurate evaluation of different treatment strategies and 

maintenance operations. 

Transportation Outcome(s): The primary benefit will be improved safety and mobility of the 

traveling public. Maintenance crews will now have the ability to evaluate treatment selections 

along with timing of applications and rates. This will lead to continual reevaluation of current 

Figure ID-1. RWIS installation at 

Goose Creek Summit on State 

Highway 55 in central Idaho.
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BMPs to continue the trend of reducing ice-up time. The new BMPs are anticipated to reduce 

time and materials for storm event clean up and better utilize resources. Anticipated cost 

savings from new BMPs will allow ITD to expand the RWIS network allowing other areas to reap 

the rewards of the RWIS data and expand the system to additional locations. 

Implementation Issues: Receptiveness to the system across ITD was rather low upon the first 

year of statewide implementation. As the winter season progressed and the RWIS locations 

became more reliable and acceptable, the performance measures gained momentum. Funding 

was an issue initially, but with the acceptance of the system came a reevaluation of intelligent 

transportation system (ITS) projects; funding was redirected into the RWIS Performance 

Measurement and Reporting (PMR) upgrades. All 87 RWIS stations are anticipated to be PMR 

ready by fall of 2012. New sites are being discussed and programmed by the districts to 

continue the expansion process. The districts have submitted request for a complete statewide 

build out of a total of 140 PMR sites.

Contact(s): 

• Dennis Jensen, Idaho Transportation Department - Mobility Services-Winter Maintenance 

Coordinator, Office 208-334-8472, Cell 208-901-1100, dennis.jensen@itd.idaho.gov

• Ed Bala, Idaho Transportation Department – District 5 Engineer, Ed.Bala@itd.idaho.gov

Keywords: performance measure, ice-up time, grip coefficient, surface temperature, and best 

maintenance practices.
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Iowa DOT Salt Use Dashboard

Spreading salt on road surfaces is one of the primary means for removing and preventing 

accumulation of snow and ice. The Iowa Department of Transportation (Iowa DOT) has a new 

management dashboard featuring actual salt usage during maintenance operations compared 

to estimated usage amounts, based on road weather conditions. Managers monitor this 

Dashboard to make sure current usage is reasonable given the weather and is within Iowa 

DOT’s standard application rate guidelines. Development of this Dashboard is very recent, with 

implementation occurring in August 2011 before the start of the winter season. Already, the tool 

is encouraging and allowing maintenance staff to keep a tighter control on salt usage. 

System Components: As seen in Figure IA-1, the salt use dashboard consists of the following 

elements:

• State, district, and garage-level displays

• Color-coded dials indicating actual salt usage versus the targeted usage

• Interactive graphs and charts to view area and time period of choice

• Salt purchasing status

• Comparisons to estimated ‘target’ use, based on storm weather information

• Comparisons to budget availability

• Daily, Pay Period, or Year-to-Date summaries

Figure IA-1. Example screenshots from the Iowa DOT Salt Use Dashboard.
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System Operations: There are several inputs to the Dashboard to generate the usage 

visualizations and outputs which aid managers in their decision making. Road temperature 

information from Road Weather Information Systems (RWIS) is merged with winter storm 

information from standard crew reports. This weather information helps to estimate salt use 

rates. These rates are based on Iowa DOT salting guidelines, as derived from the “Guide for 

Snow and Ice Control” published by the American Association of State Highway and 

Transportation Officials. Garage responsibility-miles and service requirements information 

modify the basic rate estimates (in total salt per lane-mile) into a garage-specific daily total

tonnage. 

The Dashboard accesses the actual usage information and the weather-based estimates from a 

database and displays it in the dashboard application. Dashboard information is rerun every 

week and distributed to management and garage supervisors via email. Currently, the 

Dashboard is built in Microsoft Excel. There are plans to convert it to commercial dashboard 

software in summer 2012 for release prior to the winter season. 

Transportation Outcome(s): The Salt Use Dashboard helps Iowa DOT ensure that salt usage 

and labor usage compares favorably with department guidelines. This helps provide a uniform 

and predictable level of service, and keeps costs within budget. It can also be used to identify 

practices that seem to provide better service with less salt.

Implementation Issues: Sometimes when maintenance actions adhere to the recommended 

salt usage rates the desired level of maintenance and service is not obtained. Iowa DOT is still 

investigating these cases to determine whether the guidelines are inadequate or if maintenance 

practices need to be altered. It is also still unclear how the usage rates should be modified for 

different levels of service or traffic volumes.

Contact(s): 

• Tina Greenfield, Iowa DOT RWIS Coordinator, 515-233-7746, tina.greenfield@dot.iowa.gov

• Annette Dunn, Iowa DOT Winter Operations Administrator, 515-239-1355, 

annette.dunn@dot.iowa.gov

Reference(s): 

• Transportation Research Board, 2004. NCHRP Report 526, Snow and Ice Control: 

Guideline for Materials and Methods

<http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_526.pdf>

• AASHTO, 1999, Guide for Snow and Ice Control

<https://bookstore.transportation.org/Item_details.aspx?id=1019>

Keywords: asset management, salt use, dashboard, maintenance
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Iowa DOT Weatherview Road Weather Traveler Information 

System

The Iowa Department of Transportation’s (Iowa DOT) “Weatherview” website is an example of 

real-time road weather information provided for the traveling public. “Weatherview” was made 

available online in 1999. The current site was released in 2009. Subsequently, it has been 

updated to incorporate road cameras, traffic flow information, and maintenance tools like email 

and mobile-text alerts triggered by certain weather events. Additionally, plow truck locations 

obtained via Global Positioning Satellites (GPS) are reported to personnel with Iowa DOT 

viewing permissions.

System Components: The “Weatherview” system consists of the following elements:

• A main map to display and overlay information from Road Weather Information System 

(RWIS) stations and information from Automated Weather Observation Systems 

(AWOS), as shown in Figure IA-2

• Site-specific forecasts to aid in road maintenance, along with historical weather graphs 

and charts

• Camera image gallery

• Rural traffic speed information

• Features that allow Iowa DOT-authorized personnel access to

o Email alert subscriptions based on site observations,

o GPS and Automated Vehicle Location (AVL) data showing current truck locations 

and plow/spreader information,

o Work status of winter maintenance crews around the state.

Figure IA-2. “Weatherview” website showing RWIS and AWOS site locations.
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System Operations: The “Weatherview” site is hosted by Iowa DOT and retrieves current 

AWOS and RWIS information from the department’s databases. Google Maps software is used 

to manage map display functionality. The site retrieves Iowa DOT GPS and crew status map 

layers from Iowa DOT’s Geographic Information System (GIS) map services system. 

Transportation Outcome(s): The “Weatherview” system enables easy access to real-time, 

useful weather information to travelers, Iowa DOT maintenance crews, local agency 

maintenance crews, and the general public. This information is used to make treatment 

decisions, is shared with airport commissions to help organize flight plans, helps to monitor road 

conditions and traffic flow in inclement weather, and aids in planning daily travel or activities. 

Implementation Issues: The new “Weatherview” website contains more high-bandwidth 

products than the original, especially Google mapping and camera images. The site has 

required more server capacity in order to provide quick and reliable information to the thousands 

of users that access it during a storm. The additional advanced functionality also makes it more 

complicated than the original site, requiring more information technology support staff to 

maintain it.

Contact(s): 

• Tina Greenfield, Iowa DOT RWIS Coordinator, 515-233-7746, 

tina.greenfield@dot.iowa.gov

• Annette Dunn, Iowa DOT Winter Operations Administrator, 515-239-1355, 

annette.dunn@dot.iowa.gov

Reference(s): 

• Weather View website <http://weatherview.iowadot.gov>

Keywords: Road Weather Information, travelers, website, real-time, mapping
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Kansas City Scout Advanced Traffic Management System

Kansas City Scout (KC Scout) is a comprehensive traffic congestion management and traveler 

information system conceived, designed, and operated jointly by two Departments of 

Transportation. In September of 2001, the Missouri Department of Transportation (MoDOT) 

and the Kansas Department of Transportation (KDOT) jointly announced their bi-state initiative 

to address traffic impacts on over 100 miles of contiguous freeways intersecting both sides of 

the state line throughout the greater metropolitan Kansas City area. Kansas City Scout 

encompasses the jurisdictional boundaries of Cass, Clay and Jackson counties in Missouri and 

Johnson County and Wyandotte County in Kansas. 

Providing the core platform for Scout’s Transportation Management Center (TMC) operation is 

its state-of-the-art TransSuiteTM Advanced Traffic Management System (ATMS). Within this 

framework, Closed Circuit Televisions (CCTVs), Dynamic Message Signs (DMS) and Vehicle 

Detection Stations (VDS) are controlled and monitored. Commencing operations in summer 

2011, this system integrates weather information with the pre-existing traffic management 

capabilities of KC Scout. The integrated system was tested during winter 2011 and into the 

summer months. Evaluation will continue through April 2013 in order to capture data for two 

complete seasons.

Prior to September 2009, Scout used a UNIX-based system that provided little support for 

enhancement development, report generation or operator efficiency. Many manual 

workarounds were developed by Scout staffs that were time consuming to create and maintain 

but provided the level of utility desired to create and monitor incidents, track activity, and provide 

management reporting capabilities. Inbound weather information consisted of daily MoDOT 

radio broadcasts of WeatherOrNotTM furnished forecasts or Internet-based weather media 

channels monitored on individual desktops. Scout operators became adept at identifying 

changing weather conditions while constantly monitoring CCTV cameras spanning over 100 

miles of interstate in the metro KC area. 

With the recent upgrade to ATMS, Scout is able to integrate weather information into the user 

interface as another “layer” utilizing the data available from external weather information 

sources, such as National Oceanic and Atmospheric Administration (NOAA), National Weather 

Service’s (NWS) National Digital Forecast Database (NDFD), and Meridian-511 providers. 

System Components: The KC Scout TMC was completed and opened in late 2003. It is an 

integrated system of 138 CCTVs, 38 DMS, 277 VDS, a highway advisory radio (HAR) system 

and a dynamic web site offering users the capability of designing their own customized alert 

messaging profiles. The user-interface utilizes a series of “layers” that visually represent 

infrastructure (CCTVs, DMS, VDS), traffic incidents, scheduled events (roadwork) and special 

events (heavy traffic stadium/concert events). The new ATMS software binds the various 

sensing components, communications infrastructure, weather information, and user interfaces.

System Operations: The Windows/SQL-based TransCoreTM product has streamlined all the 

processes associated with creating and monitoring traffic incidents, activating and updating 

DMS message boards and linking all pertinent incident information – including weather – into 

easily accessible databases and reporting tools. 

As an example, when a weather condition exists that meets pre-selected alert threshold criteria, 

a “layer” will “activate” on the operator’s ATMS desktop map application, signaling creation of a 
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weather event type “incident” with applicable DMS messaging and outputs to Scout’s website 

and subscriber-configured WebAlert applications.

Furthermore, during winter storm events, MoDOT’s traffic department staffs a separate 

workstation within the TMC, solely for the purpose of monitoring road conditions and reporting 

on the snowplow activity within its local coverage area. This is of great assistance to KC Scout 

operations because the information can be used to post DMS messages in advance of the 

plows, helping to keep those lanes clear of through traffic that would otherwise impede plowing 

activity.

Transportation Outcome(s): The quickness of being able to notify motorists of a rapidly 

developing severe weather condition will aid in their decision making and hopefully reduce 

severe weather related crashes on the interstate. It is expected that this system, with its 

enhanced and integrated weather information, will result in timelier messaging for the traveling 

public, along with more proactive internal sharing of weather information between operations 

and maintenance, and will result in improved highway performance and traveler safety. Figure 

KC-1 further details benefits from the system.

Figure KC-1. Kansas City Scout's ATMS integrated with weather information.

Implementation Issues: There are several ongoing concerns for operation and implementation 

of the system. It is critically important that the integrated ATMS system is fully operational, 

including functional DMS and CCTVs, for example. Also, operators need to be properly trained 

in the use of any new components associated with the acquisition, integration, processing and 

dissemination of weather information.

In regards to the recent software transition, the Windows/SQL-based TransCoreTM product 

deployment was nearly seamless. Training on the use of these new elements required TMC 

staff development along with support system documentation.
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Contact(s): 

• Jason Sims, Traffic Center Manager for KC Scout ATMS, jason.sims@modot.mo.gov

• Nancy Powell, TMC Supervisor, KC Scout, nancy.powell@modot.mo.gov

Reference(s): 

• RITA Intelligent Transportation Systems Joint Program Office, February 2011. Weather 

Information Integration in Transportation Management Center Operations, Final Report, 

FHWA-JPO-11-058, February 2011

<http://ntl.bts.gov/lib/38000/38600/38677/TMC%20Final%20Report%20Website%206.1

3.11/tmc_integration_report_final.pdf>

Keywords: traffic management, software, transportation management center, road weather 

information system, customized alerts, Kansas City
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Kansas DOT Road Weather Information for Travelers System

The Kansas Department of Transportation (KDOT) Road Weather Information for Travelers 

System shares road condition information with the traveling public in Kansas. This information 

is used for making travel decisions before travel commences and during travel. Initially, the

information was provided by a road condition website, known as KanRoad, and a toll-free 

hotline that provided periodic information and required manual recordings about general 

road/weather condition information. 

In 2000, the United States Department of Transportation was granted the 511 number for 

disseminating traveler information. Additionally, the Federal Highway Administration made 

funding available that helped KDOT evaluate its traveler information system for content, 

method/frequency of delivery, cost, accuracy and reliability. KDOT decided to deploy a 

Statewide 511 System that would ultimately provide significant improvements over the existing 

KDOT hotline used during the winter months. 

The Kansas 511 System was deployed in January 2004 and is a fully automated system that 

provides near real-time route and segment-specific information for state highways and Interstate 

highways. Kansas 511 is also fully interoperable with the Nebraska 511 System, so callers 

may also get complete information regarding Nebraska highways, and vice versa. Phone 

numbers are provided for roadway information in all other states adjacent to Kansas. 

Information provided includes road conditions, work zones, closed lanes, ramps or roads, 

incidents, major events, emergency travel information and weather, including route/segmentspecific “now casts” and forecasts for up to six hours.

In 2009, KDOT launched KanDrive, <www.kandrive.org>, a one-stop gateway for travel 

information in Kansas and surrounding states. Content includes weather-related driving 

conditions, work zones, traffic incidents and weather information through a variety of 

communication media. It also provides travelers with other helpful travel information as noted 

below. Site features include:

• Interactive, online color-coded 511 Map (KanRoad re-branded to 511) that provides 

statewide, regional and metro area (Kansas City, Topeka/Lawrence, or Wichita) views.

• Camera views (both still and motion views for some locations)

• Current messages on Dynamic Message Signs

• Road Weather Information System (RWIS) map; National Weather Service 

Watches/Warnings and weather-related safety travel information

• Links to other helpful travel information, including metro traffic information for Kansas 

City and Wichita, data from roadway weather stations (RWIS), neighboring states’ travel 

information, the Kansas Turnpike Authority (KTA), maps of the state, counties and cities, 

services for over-the-road truckers, and tourist information.

System Components: The KDOT Road Weather Information for Travelers System consists of 

the following:

• 511 phone system

• 511 Map <511.ksdot.org> that provides travel information similar to that provided on the 

511 phone system

• KanRoad System within KDOT that provides the data for the 511 phone system and 511 

Map
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• KanDrive web site (a travel information portal) found on the KDOT general web site, 

<ksdot.org> or directly accessible from <www.kandrive.org>. This includes links to KC 

Scout, WICHway, Amber Alert, and the 511 Map.

• 511 Mobile Website <511mm.ksdot.org>

• Road Weather Information System (RWIS) maps that display atmospheric weather and 

pavement sensor data received from KDOT’s remote processing units that are 

positioned strategically across the state.

• Wi-Fi/KIOSKS (planned) at KDOT Rest Areas, Travel Information Centers and State 

Parks

• Snow gates along I-70 that are currently operated manually when deployed. Prior to 

snow gates, barricades were utilized. 

System Operations: The system includes road condition information gathered by KDOT staff. 

Typically this is the road superintendent, supervisor or office staff, culling information from 

equipment operators. Using staff at these levels has provided consistency that was lacking with 

initial efforts using equipment operators only.

KDOT is contracted with Meridian Environmental Technology to provide weather forecasts for 

the Kansas roadways on the 511 Phone System and with Telvent DTN to provide weather 

forecasts to Statewide KDOT field decision makers. Weather conditions include snow, ice, hail, 

thunderstorms, winter storms, fog and burning. Flooding is reported as a roadway event. 

Usage of the phone and website is year round, rather than solely focused on the winter.

All information provided on the 511 Phone System and 511 Map is fully automated, following 

initial manual data entry. Information is updated in the system within 5 minutes of data entry. 

Improvements to the system are based on information developed in the formation of a strategic 

plan, acknowledging resource constraints. Annual improvements, whether large or small, must 

be completed prior to the start of the winter season. This means testing must be completed by 

showing successful implementation of new features prior to October 1. 

A KanDrive Support Plan has been developed to provide important procedures, documentation 

and consistent, efficient communications for KDOT, at both headquarters and District staff 

levels. The plan includes not only procedures during business hours, but also for after-hours 

operations and communications.

Transportation Outcome(s): The KDOT Road Weather Information for Travelers System is able 

to provide road conditions, weather, and lane or road closures due to construction, 

maintenance, or incidents. An informed traveler is able to make decisions that are safer while 

providing optimum mobility. Today’s travelers expect this content and a range of delivery 

modes to be available to them in Kansas.

Implementation Issues: Initial deployment challenges included working with landline and cell 

phone companies across Kansas. Initial work included engaging the assistance of the Kansas 

Corporation Commission. This work was critical in the development of the 511 phone system.

Developing the “behind the scenes” weather condition-gathering system included the assistance 

of a Working Group, and significant contributions from field staff. This development activity has 

been modified so as to provide more consistency across the state. 

Reduced staff at KDOT has produced instances where timeliness of reporting has been 

affected. For example, the person who plans to enter the conditions may have to assist with 

plowing operations, which diminishes time available for data entry. At the same time, Districts 
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have aided neighboring Districts with manpower to mitigate effects of weather conditions and to 

post road weather-related information on the Dynamic Message Signs (DMS).

KDOT’s urban Transportation Management Centers have aided in providing after-hour 

operations as needed for the cameras and DMS. This aids in quality and timeliness of the 

information. KC Scout’s weather integration project has also provided invaluable assistance in 

generating emergency weather messages for DMS and in coordination with 511. It has further 

assisted with coordination between the National Weather Service and other state transportation 

partners and their communications.

The list of partners needed to implement this system was comprehensive, involving several 

bureaus within KDOT and partners from other agencies or organizations such as the Kansas 

Highway Patrol (KHP). KDOT has initiated several email distribution lists that can target certain 

groups within KDOT or other partner agency personnel to facilitate efficient communications 

with all extended team members, such as operations, technology, or public affairs.

Funding has been a challenge. Limited funding sources as well as funding amounts and 

resources are not consistent from year to year. Improvements to the phone system, the web 

site, the mobile applications and remote use such as at kiosks need to be broken out into 

phased improvements. Such a strategy may not be optimal from a development standpoint.

Finally, the partners at KDOT have learned that an important function of disseminating road 

weather information is to temper the expectations that motorists have in travel times.

Contact(s):

• Barb Blue, KDOT, Advanced Traveler Information/ 511 Program Manager, 

BBlue@ksdot.org

• Troy Whitworth, KDOT, Staff Maintenance Manager, Troy@ksdot.org

• Mary Beth Pfrang, KDOT, GIS Applications Project Manager, Marybeth@ksdot.org

Reference(s): 

• 511, when called in Kansas, by either landline or cell phone, or 1-866-511-KDOT (5368) 

from anywhere in the U.S.

• 511 Map <511.ksdot.org>

• 511 Mobile <511mm.ksdot.org>

• KanDrive <www.kandrive.org>

• RWIS public site <http://www.ksdot.org/burcompser/generatedreports/weather.asp>

• KDOT Home page <www.ksdot.org>

Keywords: KDOT, KanDrive, 511, Road Conditions
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Maryland DOT Emergency Truck Parking Portal

During inclement weather, and especially during severe snowstorms, drivers of commercial 

trucks are often in need of emergency parking areas or a safe haven to “ride out” the storm. As 

a result, the Maryland Department of Transportation (MDOT) in cooperation with the Maryland 

Motor Truck Association (MMTA) and the I-95 Corridor Coalition developed and implemented a

program for emergency truck parking throughout the state of Maryland. The program includes 

the use of six (6) Park and Ride lots statewide to be used during heavy snow events as a safe 

haven for truckers. The development of a mobile application and web-based mapping to 

communicate the locations of all public facilities open for truck parking during emergency and 

non-emergency operations was also included as part of the program.

During the deployment process, the identification of emergency lots and enhanced use of 

available communication tools were proactive ways to alleviate future truck parking capacity 

issues similar to that experienced by the state of Maryland during the 2010-2011 winter season. 

To ensure safety on the state’s highways, it was determined that reliable and constant 

communication with truck drivers is imperative to ensuring efficient highway operations and 

maintenance during weather events. To accomplish this goal, Maryland developed the policy 

and set the process in motion by partnering with the state trucking association, police agencies, 

and local traffic and highway agencies. 

The timeline from concept to project execution was less than two months, and truck drivers in 

Maryland now have designated places to stop during snowstorms. The six (6) Park and Ride 

lots across the state were selected as emergency lots for truck drivers traveling through 

Maryland by MDOT, Maryland Motor Truck Association, and the I-95 Corridor Coalition.

The total cost of the emergency truck parking application was approximately $100,000.

System Components: As mentioned above, the initiative includes the use of carefully selected 

Park and Ride lots, and mobile and Geographic Information System mapping applications. 

More information is available via Internet websites, and the page displaying emergency parking 

options for trucks can be viewed by going to the State Highway Administration (SHA) website at 

<http://sha.md.gov/pages/Emergencytruckparking.aspx?PageId=856>.

System Operations: The goal of the system is to help truckers going through Maryland make 

informed decisions during snowstorms. A new "mobile app" is available to inform truck drivers of 

the six (6) emergency lots, as well as other existing lots, to be used for commercial truck 

parking. Users can download this application to their phones, which will show a web-based 

map indicating the location of regular truck parking options (shown in green), and, on the same 

map, where emergency parking options are located (shown in blue) – example in Figure MD-1.

There are two (2) emergency lots in Montgomery County, one (1) in Harford County, one (1) in 

Baltimore County, one (1) in Frederick County, and one (1) in Prince George's County. The Park 

and Ride lots include facilities operated by the SHA and the Maryland Transportation Authority 

(MDTA), which will be responsible for removing the snow on the lots. The parking options can 

also be viewed from an interactive map online or as a PDF document that can be downloaded 

and printed.
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Figure MD-1. Maryland’s emergency truck parking portal.

Transportation Outcome(s): During snowstorms of six (6) inches or more, tractor trailer drivers 

may use several commuter Park and Ride lots as a safe haven to “ride out” the storm instead of 

parking on highway ramps and shoulders, which present unsafe conditions for other highway 

users. This initiative provides an alternative for truckers traveling during heavy storms. The 

mobile application and web-based mapping tools provide the location of all truck parking areas 

available to truck drivers and company dispatchers, which facilitates preparedness when 

traveling in (and through) the state of Maryland.

Implementation Issues: One of the challenges faced during implementation was understanding 

the maintenance requirements of the public parking lots and determining whether truck parking 

would impede maintenance processes. The original list of potential emergency truck parking 

sites included 20 locations statewide, but facilities maintenance and geometric constraints 

reduced this number to six (6) sites to be used during the 2011–2012 winter season and 

thereafter. Another challenge was the inability to properly assess the results of the pilot 

program during the 2011–2012 winter season, which was largely due to the mild weather 

experienced in the Mid-Atlantic region. 

Contact(s):

• Debbie Bowden, Freight and Economic Policy Analyst, Office of Freight and 

Multimodalism, Maryland Department of Transportation, 410-865-1094, 

DBowden1@mdot.state.md.us

• Michael Baxter, Division Chief, Highway Information Services Division, Office of 

Planning and Preliminary Engineering, Maryland State Highway Administration, 410-

545-5511, MBaxter@sha.state.md.us

•
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Reference(s): 

• Maryland Emergency Truck Parking Portal website

<http://sha.md.gov/pages/Emergencytruckparking.aspx?PageId=856>

Keywords: Truck parking, emergency truck parking, truck parking communication
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Michigan DOT Measurement of Regain Time

The Michigan Department of Transportation (MDOT) spends roughly $100 million on winter 

maintenance each season. This represents approximately forty percent of its total maintenance 

budget. With this significant expenditure, there is a need to find an effective performance 

measure that will allow MDOT to evaluate the effectiveness of changes to its operations and to 

communicate this with the public.

For the winters of 2009-12, MDOT has collected speed information along the Interstate 96 (I-96)

corridor from the Ionia County line eastward to the Oakland County line. Portable microwave 

sensors are used to detect traffic speed before, during and after a winter storm event. This 

information is then downloaded and graphs are prepared to show the average speeds over 

time. In addition, storm start times and end times are recorded by maintenance staff along with 

other information about the intensity and temperatures during the storm. The data are then 

used to illustrate regain time, which is the time needed after a winter storm event until vehicle 

speeds return to normal operating speeds.

System Components: The main components of the system are three microwave sensors that 

detect the speed of the traffic along the I-96 corridor. The sensors are spaced such that each is 

collecting information from a segment of interstate maintained by different MDOT road 

maintenance garages. Figure MI-1 illustrates a typical sensor apparatus.

Two of the sensors have a wireless signal that 

allows MDOT to remotely download the data 

from the office. The third sensor does not 

have Internet capability so the data is 

downloaded manually through a computer 

cable.

In order to sustain power to the sensors, each 

unit is hooked up to a Pointer Record (PTR)

station that has a constant power 

source. During winter months, the solar 

panels do not generate enough power for the 

sensors to work. A power hook-up is needed.

System Operations: Two of the microwave 

sensors are mounted on portable trailers while 

the third is a portable unit that is attached to a 

power pole adjacent to I-96. The Microwave 

Vehicle Detection System (MVDS) High 

Definition Sensors use Wavetronix software 

for communications. This software is freely 

downloaded from Wavetronix with the 

purchase of the equipment. 

Once MDOT receives the data it will need to be filtered through to match up with the storm 

events and analyzed. Some of this data is also shared with the Planning division since we 

collect all the lanes that we can along with speed, volume, occupancy, truck percentages, and 

85% speeds. 

Figure MI-1. Speed sensor apparatus to 

determine regain time.
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Transportation Outcome(s): Speed seems to be one of the best indicators of effectiveness of 

MDOT’s winter maintenance operations. The motoring public values the ability to move at 

posted speeds and have minimum delay. Assuming speed measurements are the best 

indication of regain time, the system can be scaled up to determine regain time for any areas 

with valid speed data. Speed data is already generated on most state freeways by the mobile 

phones of participating motorists. Additionally, other areas have various detection devices 

which capture speed data.

Implementation Issues: The use of portable traffic collection trailers is challenging given the 

winter conditions typically experienced in Michigan. MDOT found that the collection trailers 

would not adequately recharge with use of solar panels. The trailers had to be powered with a 

direct connection to the electrical power grid, eliminating many potential monitoring areas along 

the roadway. In addition, the cell phone connection used for data transmission has not always 

been reliable. These issues should be resolved once MDOT begins using speed data from 

mobile phones and other sources.

Contact(s): 

• Will Thompson, Michigan DOT, Associate Region Engineer - University Region, 517-

937-8672, thompsonw@michigan.gov

Reference(s): 

• Foley, J., Thompson, W., and Warren, R., August 2009. “The Use of the 85 Percentile 

Speed Data as a Measure of Winter Maintenance Performance,” presented at the 2009

National Rural ITS Conference

<http://www.nritsconference.org/downloads/Presentations09/S5_Foley.pdf>

Keywords: regain, speed, microwave, wireless, winter, maintenance
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Figure MN-1. 

ATM signals on I-35W.

Minnesota DOT I-35W Smart Lanes: Active Traffic 

Management

Minnesota’s Smart Lanes is the brand name of the Active 

Traffic Management (ATM) system on I-35W in the Twin 

Cities Metro Area. The ATM system was deployed on 

Interstate 35 West (I-35W) in two phases between 2009 and 

2010. The original system covered sixteen miles of I-35W 

south of Minneapolis and was extended by two miles in 

2011. A new eight-mile section of ATM is being installed on 

Interstate 94 (I-94) between downtown Minneapolis and 

downtown St. Paul and was scheduled to be activated in the 

summer of 2012.

ATM consists of electronic signs over lanes of traffic (see 

Figure MN-1) to provide real-time information to help 

motorists make informed decisions about their commute. 

The signs display information about road conditions to 

improve traffic flow, reduce congestion and improve safety.

The signs are illuminated during traffic incidents to indicate 

whether lanes are open to traffic. This use of technology will 

enhance safety and improve the flow of traffic by providing motorists information about the 

conditions within their lane (and alert them to what is ahead). The information provided by these 

overhead lane signs will be real-time, designed to help motorists navigate safely through traffic. 

The ATM system was modeled after similar systems in Europe that have been proven effective 

at reducing collisions and improving traffic flow.

The ATM system is operated out of the Regional Transportation Management Center (RTMC). 

The RTMC is a co-located operations center housing Minnesota Department of Transportation 

(MnDOT) freeway management staff, Freeway Incident Response Safety Team (FIRST) 

dispatch, MnDOT arterial management staff, MnDOT maintenance dispatch, and State Patrol 

metro area dispatch. From the RTMC, MnDOT operates a Freeway Management System 

(FMS) covering over four hundred miles of Twin Cities Metro Area freeways including the I-35W 

ATM corridor. The system includes loop detection, dynamic message signs (DMS), ramp 

meters, cameras, and fiber optic communications. The existing FMS provided the backbone for 

the ATM system deployed on I-35W.

MnDOT has a freeway traffic management system software known as Intelligent Roadway 

Information System (IRIS). IRIS was developed in-house to communicate and control loop 

detectors, DMS, and ramp meters. The software was expanded to control the ATM system.

System Components: A series of overhead signs known as Intelligent Lane Control Signals 

(ILCS) above each lane on I-35W are used to inform drivers of upcoming conditions or controls 

in place. Overhead signs are used to indicate which lanes are closed to access, blocked 

because of a crash or obstruction, and which adjacent lanes are impacted by such events. The 

ILCS are used to post advisory speed signs, warning travelers to slow in anticipation of stopped 

traffic ahead.
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Figure MN-2. Possible display 

messages above traffic lanes.

The ILCS are located along northbound and southbound I-35W from I-35 to the I-35W split with 

Highway 65. Spacing of the signs is approximately one-half mile apart. The exact spacing is 

based on relations to bridges, existing signs, sight lines and budgets. 

Existing overhead signs and High Occupancy Toll (HOT) lane signs are incorporated on same 

sign structures as ILCS. Sign structures are placed in accordance with sign spacing 

requirements. Sign structure placement will be determined in the design stage.

At key locations along I-35W, ILCS are used to inform drivers of closed lanes and/or 

recommended speed limits. The managed lane control system essentially serves four key 

purposes:

• Inform drivers when the left lanes are open to High Occupancy Vehicle (HOV) and/or HOT 

lanes;

• Inform drivers of advisory speed limits (when necessary) in order to slow traffic that is 

approaching stopped traffic (At this time, uniform speeds are posted across all lanes. 

MnDOT has not ruled out the idea of varying speeds in lanes and may opt to implement this 

in the future); 

• Inform drivers of lanes closed (such as when dynamic shoulder lanes are closed or when 

general purpose lanes are closed due to a crash or stalled vehicle); and

• Inform drivers of hazards such as standing water or debris on the roadway and encouraging 

travelers to merge away from the hazardous lanes.

The signs over each lane are used to display one of eight messages, as shown in Figure MN-2 

and summarized as follows:

1. Blank (black sign) – to be used as the default display. 

To be effective ILCS messages should be timely, 

accurate, and reliable. Displaying other default 

messages would distract from normal signing and 

would dilute effectiveness when really needed. 

2. Red ‘X’ – to be used to indicate that the lane is closed 

to traffic or has an incident, crash or other obstruction. 

Emergency vehicles and other incident responders 

would be allowed to use the lane to respond to 

blocking incidents quicker.

3. Advanced Yellow ‘X’ – to be used to indicate that the 

lane will be closing one mile ahead because of an 

incident, crash, or other obstruction.

4. Merge with moving chevron – to be used to indicate 

traffic should merge right or left as the lane is closed 1⁄2 

mile ahead because of an incident, crash, or other 

obstruction.

5. Yellow Flashing Arrow – to be displayed on lanes 

adjacent to a closed lane (each Red ‘X’ will be 

surrounded by yellow flashing arrows.)

6. Green Arrow – to be displayed during an incident 

above those lanes not affected by the incident (a red 

‘X’ will be above the lane with the incident, flashing 

yellow arrows above adjacent lanes, and green arrows 

above other lanes.)

7. Advisory Speed – displayed as a two-digit number with ‘MPH’.
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Figure MN-4. Display of advisory speed limits 

on DMS as it relates to freeway speeds.

8. White diamond – to be used to indicate lane use as exclusively for 

vehicles with high occupancy.

System Operations: The managed lanes are controlled by RTMC operators from within the 

RTMC. Operators have full authority to select from available messages, after events are 

verified. 

The display of lane advice depends on the location of any lane obstructions and the resulting 

Red ‘X’ signal indicating lane closure. Advanced warning messages are posted on all signs 

located upstream of the blockage within a distance of at least one mile. As motorists approach 

a closed lane they will encounter an Advanced Yellow ‘X’ sign one mile before the closure. The 

next sign will display a ‘Merge with Arrow’ within a half mile of the actual Red ‘X’ sign over the 

lane that is closed. This is to ensure that travelers have advanced warning of the closure before 

reaching the incident. Further upstream, the signs will display an automated advisory speed 

posting which will change based on real time traffic conditions. This is explained in the next 

section.

When display signs are posting either a Red ‘X’ or yellow flashing arrow message, all other 

signs will display a green arrow. Figure MN-3 shows an example of signing for a crash blocking 

a lane and activating Advisory Variable Speed Limits.

Figure MN-3. Example of display of intelligent lane control signals during an incident.

The selection of advisory variable speed limits (VSL) is computed by an algorithm developed by 

the RTMC and the University of 

Minnesota - Duluth. RTMC operators 

have the option to override the 

calculated advisory speeds or to accept 

the recommendation and verify the 

posting of the message. 

The goal of the advisory VSL system is 

to mitigate shock wave propagation from 

downstream bottleneck by gradually 

reducing speed levels of incoming traffic 

flow. Figure MN-4 illustrates how speed 
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data is collected through traffic sensors on the roadway at point locations shown as black circles 

on the chart. Without advisory VSL, vehicles approaching congested traffic are forced to 

change speeds within a very short distance leading to sudden stopping and possible rear end 

collisions. The advisory speed limits are posted to allow for a more gradual deceleration 

between upstream free-flowing traffic and congested traffic. The speeds displayed on the ILCS 

would gradually reduce traffic speeds as shown by the yellow boxes in the figure.

As congestion levels develop, two or three sets of signs prior to the congestion display an 

advisory speed limit based on the algorithm depending on what the speed differential is 

between upstream and downstream traffic. Speeds can be posted up to 1.5 miles upstream of 

congestion. 

Advisory speeds posted to the overhead signs change by no more than five miles per hour 

(MPH) with each change in speed, and can be updated every thirty seconds if traffic conditions 

warrant. The minimum advisory speed displayed is thirty MPH and the maximum advisory 

speed displayed is fifty MPH. If the current speeds on the roadway are below thirty MPH the 

signs will go blank. 

Transportation Outcome(s): This use of technology will enhance safety and improve the flow of 

traffic by providing motorists information about the conditions within their lane (and alert them to 

what is ahead). 

Implementation Issues: There are currently several implementation issues that MnDOT is 

resolving, particularly with regards to expanding the ATM from incident-based traffic 

management to weather-based traffic management. Additionally, dynamic lane striping and 

signaling was a challenge in implementing the full system.

MnDOT is currently researching how to modify the advisory speed limit during inclement 

weather. Currently the system uses a constant deceleration rate to determine advisory speed 

limit values. Observations of the system have found that the preferred deceleration rates may 

be different during different kind of weather conditions. An observation of the system found that 

the maximum speed value needed to be adjusted due to weather conditions. Historically, the 

maximum speed limit of the system was capped at 5 MPH less than the posted speed limit. 

This value was changed to a maximum of 50 MPH for all corridors when it was found that the 

system would deploy 60 MPH on the corridor during major snow events. MnDOT is working to 

develop new techniques for the advisory variable speed limit system during weather events that 

would automatically adjust the deceleration rate and the maximum speed value based on realtime weather conditions on the corridor. The VSL system would utilize rain sensors on the 

corridor to inform the system of what type of precipitation was falling and at what rate.

Along the southern half of the I-35W corridor there are sections where the left lane of traffic was 

shifted onto the inside shoulder by two feet to allow for a buffer zone between the new HOT 

lane and the general purpose lanes. This inside shoulder was originally designed to allow for 

some ponding during heavy rainfall. Now that traffic is shifted onto these shoulders, there is a 

potential for hydroplaning during heavy rainfall as the shoulder area begins to fill up with water. 

MnDOT is investigating the use of rainfall sensors to automatically deploy either a warning 

message or advisory speed limit over this lane during these conditions.

The physical width of the stretch of I-35W northbound from 42nd Street to downtown limits the 

number of lanes and shoulders. The I-35W ATM system includes the concept of a dynamic 

shoulder lane in the left-most lane along this stretch of road. This left-most dynamic shoulder 

lane operates as a 
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Figure MN-5. Static sign 

for dynamic shoulder lane.

• priced dynamic shoulder lane at times when the adjacent stretch of I-35W is operated as a 

HOT lane,

• priced dynamic shoulder lane at times when the capacity is needed, and 

• shoulder when needed.

The dynamic shoulder lane is separated from the general 

purpose lanes by a single solid yellow stripe. An additional 

yellow stripe was placed along the center median barrier to 

improve visibility. A static sign is placed at the beginning of the 

dynamic lane (Figure MN-5).

A computer simulation of the dynamic shoulder lane entrance 

indicated that MnDOT needed to enhance the pavement 

marking to inform motorists whether the priced dynamic 

shoulder lane (PDSL) was opened or closed. For this reason it was determined that in-roadway 

lighting was best suited for this project. In the transition zone, an LED in-roadway lighting 

system was developed to alert traffic to merge right when the PDSL is closed (Figure MN-6). 

The LED lights were the same color as MnDOT’s standard yellow striping and were dimmable 

for night time driving. The in-roadway lighting was able to be changed to a white LED light when 

the PDSL is open that will extend the existing white skip striping into the dynamic shoulder lane 

(Figure MN-7). After two seasons, the LED in-roadway lighting system failed due to corrosion in 

the power connections within the LED units. Analysts compared violation rates of the PDSL 

merge area with and without the in-roadway lighting and found no distinguishable difference in 

the amount of violators in the PDSL without the lights. Due to the high cost of replacing the 

system, MnDOT is not planning to bring the LED in-roadway lighting back into service.

Figure MN-6. Striping and signing with PDSL closed.

◊

PDSL - CLOSED

38 46 th St th St 42nd St

◊

35th St 28th St

1 MI

X

XXX

26th St

X

**

** The dotted yellow line between 42nd and 38th Street represent the in-road lights. 

The lights will be spaced to simulate the painted yellow edge line.
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Figure MN-7. Striping and signing with PDSL open.

Lane widths for the dynamic shoulder lane and the general purpose lanes vary from 11 feet to 

12 feet. Between the dynamic shoulder lane and the general purpose lanes is a two foot buffer. 

Reaction distance from the dynamic shoulder lane to the center median barrier varies from 2.5 

feet to six feet. Static signing as shown in Figure 4 together with intelligent lane control signals 

will designate when the shoulder lane is open to traffic.

After the first several snowfalls, MnDOT Maintenance staff recommended that the dynamic 

shoulder lane remain open during snow and ice events to help spread the de-icing material 

throughout the lane. During off-peak periods when no vehicles were present on the dynamic 

shoulder lane, de-icing materials were not able to be spread out by passing vehicle traffic thus 

leaving icy patches across the lane. By leaving the lane open to traffic, just enough vehicles 

used the lane to keep de-icing materials spread out and keep the lane free of ice.

Contact(s):

• Brian Kary, Freeway Operations Engineer, 651-234-7022, brian.kary@state.mn.us

Reference(s):

• Minnesota Smart Lanes website <http://www.dot.state.mn.us/smartlanes/>

Keywords: Dynamic Message Sign, traffic management, incident management, weather 

management, incident response, intelligent signage, variable speed, variable lane configuration, 

advisory speed, dynamic pricing, dynamic shoulder 

◊

PDSL - OPEN

38 46 th St th St 42nd St

◊

35th St 28th St









MPH

40

MPH

40

MPH

40

MPH

40

MPH

45

MPH

45

MPH

45

MPH

45

Congested Traffic

26th St



*

* The dotted white line between 42nd and 38th Street represent the in-road lights.

The lights will be spaced similar to the painted broken white lines in the other lanes.
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Montana DOT Equipment Vehicle Management System

The Montana Department of Transportation (MDT) developed an Equipment Vehicle

Management System (EVMS) to provide a comprehensive solution for managing, monitoring, 

and controlling fleet operations for both the State Motor Pool and the Equipment program. In 

developing the system several essential principles were considered, including: preserving the 

fleet through timely servicing; conducting preventive maintenance and repairs; recording 

equipment rental rates and financial information; identifying impending fleet repairs to reduce 

downtime; maintaining an equipment replacement log that identifies equipment age and 

maximum lifetime; ensuring efficient and economical use of the fleet and manpower; and 

purchasing vehicles and equipment that are multifunctional and that will support maintenance, 

engineering, construction and other user requirements. EVMS is utilized by 16 mechanic shops 

statewide.

System Components: The EVMS is 

comprised of four modules: Labor 

Equipment; Materials; and System, as 

software application window illustrated in 

Figure MT-1.

The Labor Module performs all functions 

related to the assignment of personnel. 

Capabilities include transferring employees 

across administrative units, setting up 

crews, defining a calendar from which to 

create time cards, and the creation of 

administrative work orders.

The Equipment Module handles any and all 

equipment activity. The functionality 

includes purchasing, repairing, fueling, 

servicing, and sale/salvage for all equipment. 

 

The Materials Module provides a system for the management of material resources. These 

include capabilities for tracking material stockpiles, purchasing new supplies, managing the 

warehouse inventories, and requesting materials from other administrative units. 

The System Module controls settings of the software and maintains settings for system 

interfaces (like fuel transactions, for example).

System Operations: MDT mechanics maintain equipment through preventative measures and 

necessary repairs. When using the EVMS to catalog work performed, the mechanic selects the 

Equipment Module, and specifies the particular issue and notes an in-house repair. To 

establish a repair order, the mechanic selects the unit/vehicle number and proceeds to process 

the repair by selecting the work activity, entering labor hours per activity, listing parts used, and 

checking warranties. Down time is also recorded. Once the repair order is completed the 

mechanic signs-off and it is ready for the approval of the shop superintendent.

Transportation Outcome(s): The EVMS system manages all aspects of maintaining and 

preserving the State Motor Pool fleet and Equipment. The benefits of utilizing EVMS are digital 

Figure MT-1. Montana DOT EVMS main 

application window.
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records of inventory, scheduling and tracking repair orders, tracking labor and materials cost, 

“real time” report utilization, tracking of warranties, recording fuel & mileage history, and online 

scheduling of statewide motor pool reservations. By providing these types of data, the system 

can maximize equipment lifetime, decrease maintenance and repair costs, and increase vehicle 

utilization for maintaining and constructing state roads.

Implementation Issues: The EVMS system version 3.4 was implemented in March 2004. Since 

its implementation the application has undergone minor enhancements. MDT is currently still 

using client/server architecture for the system. A project is now underway to upgrade the 

existing EVMS to a web‐based system, which will create one location and one access point for 

the entire program. 

Contact(s): 

• Michele Cheeseman, Computer Support Specialist, 406-444-9274, 

mcheeseman@mt.gov

• Jeff Gleason, Equipment Bureau Chief, 406-444-6151, jegleason@mt.gov

• Walt Kerttula, Supervisor and Financial Specialist, 406-444-6319, wkerttula@mt.gov

Reference(s): 

• Fleet and Equipment Software Solution, AgileAssets website 

<http://www.agileassets.com/solution-sets/fleet-equipment/>

Keywords: Fleet Management Systems, Fleet Software, DOT Asset Management
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Montana DOT Traveler Information System

The Montana Department of Transportation (MDT) provides extensive traveler information to 

Montana’s driving public. This information includes winter roadway conditions, highway 

construction projects, road closures, accident and incident reports, load and speed restrictions, 

and a variety of other traveler information. 

System Components: The traveler information system 

consists of a host of media including the Internet, 

Montana’s 511 phone service, highway advisory radio 

systems, road weather information stations (RWIS) 

and cameras, and dynamic message signs. 

System Operations: Detailed information is provided 

by field personnel and then entered into a database by 

division area office staff. The database runs on an 

Oracle platform and information is disseminated to the 

web and phone service. The dynamic message signs

are controlled by using a specialized control software 

package. 

Transportation Outcome(s): Traveler information 

needs continue to grow and change as new technologies become available. The information 

MDT provides is utilized by an increasing number of people, with more than a million calls to our 

511 system since deployment in 2003 and more than 14 million hits on the website annually. By 

providing travelers with accurate information through various means it allows them to make 

informed travel decisions. The benefits include avoiding excessive delays, being prepared for 

adverse weather, and determining what route best meets their needs. 

Implementation Issues: One ongoing challenge with the system is providing accurate and 

timely information. Another open question is the cost-effectiveness of utilizing portable 

hardware versus permanent hardware for data collection and dissemination of information. 

Finally, software integration amongst products built by various manufacturers has been another 

challenge.

Contact(s): 

• Brandi Hamilton, Business Operations Supervisor – Maintenance Division, 406-444-

0468, brhamilton@mt.gov

Reference(s): 

• “Road Weather Information System”, MDT Traveler Information Website, 

<www.mdt511.com>

Keywords: traveler information, winter conditions, highway construction, road closures, accident 

reports, incident reports, load restrictions, speed restrictions

 

Figure MT-2. Components of 

traveler information system.
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New Mexico DOT Dust Control System

Dust storms occur quite frequently in New Mexico. They are the result of when powerful winds 

pick up large quantities of very dry (and thus, easy to particulate) exposed surface soil and 

obscures visibility as depicted in Figure NM -1.

The low visibility detection system installed along 

Interstate 10 (I-10) at the southwest corner of New 

Mexico in what is called the La Playa Region 

(ancient dry lake bed). This stretch of I-10 is 

routinely closed due to dust storms, some of which 

have been fatal in the past. The system was 

installed at the end of 2011 as part of a technology 

transfer research project with New Mexico State 

University acting as the principal investigator. 

The research project is ongoing and currently in the 

evaluation phase (expected to continue for two years). The purpose of the system is to work in a 

coordinated fashion with other ITS deployments along I-10 (Dynamic Message Signs [DMS], 

Closed Caption Televisions [CCTV], and Highway Advisory Radio [HAR]) to assist in incident 

management (including network surveillance and information dissemination) when dust storms 

occur. The scope of the installation is limited to the immediate vicinity of the La Playa Region at 

mile points 10 and 11 of I-10. The cost of two installations was approximately $200,000. The 

installations began in October and were completed in November of 2011. 

System Components: The NMDOT La Playa RWIS 

system consists of the following specific equipment:

• Ultrasonic Wind Sensor

• Present Weather / Visibility Detector

• Air Temperature and Humidity Sensor

• Solar Radiation Shield

• Barometric Pressure Sensor

• Remote Processing Unit (Battery Backup)

• 30-foot collapsible (folding) tower

• Video Monitoring System 

• Wireless modems 

System Operations: System relies on web-interface 

for access. Collected data includes:

• Air Temperature

• Dew Point Temperature

• Wind speed

• Max Wind speed

• Precipitation with rolling averages for 1, 3, 6,

and 24 hours

• Relative humidity

• Visibility 

Data is managed, stored and accessed via Vaisala Inc. Navigator System. 

Figure NM-2. La Playa 

I-10 RWIS mile post 12.

Figure NM-1. Poor visibility on I-10 

due to dust storm.
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Power service is via standard secondary power (no solar). 

The System can provide notifications to various stakeholders (NMDOT Maintenance and 

Dispatch Staff, Law Enforcement) when parameter values for wind speed or visibility are 

exceeded. These notifications are used to place responders into high alert on the potential for 

dust storms. Should one occur, this system will be used in conjunction with traveler advisories 

via DMSs, HARs and 511 / Website and network surveillance systems at pre-determined 

closure points. 

Transportation Outcome(s): The La Playa I-10 RWIS system is still in the evaluation phase of 

the research project. Benefit and Cost criteria has been established and will be collected over 

the next two years to determine if the system is suitable and feasible for a wider deployment.

Implementation Issues: Bringing power to each of the remote installations has been the most 

substantive element of concern.

Contact(s): 

• Ruinian Jiang, Principal Investigator and Evaluator for NMSU, 575-646-1506,

rjiang@nmsu.edu

• Scott McClure, P.E., Chief of NMDOT Research Bureau, 505-798-6739,

Scott.mcclure@state.nm.us

• Charles Remkes, P.E., Manager NMDOT ITS Operations, 505-222-6554, 

Charles.remkes@state.nm.us 

Reference(s): 

• Dust Storm Mitigation White paper by NMDOT 

<http://www.dot.state.nm.us/content/dam/nmdot/Research/Profile Sheet - Dust Storm 

Mitigation.pdf>

Keywords: Dust Storms Low Visibility Warning System
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Pennsylvania DOT Interstate Restriction System

In February 2007, a winter storm comprised of rain, ice and snow caused multiple accidents on 

Pennsylvania’s interstate highway. Twenty five percent of interstate routes were closed for 

extended periods of time. Many motorists were stranded along interstate corridors. Local and 

state resources were diverted from their primary duties during the storm to remove motorists 

from traffic queues and to manage detour routes. This combination of incidents prompted the 

Pennsylvania Department of Transportation (PennDOT) to deploy a management system for 

temporary speed restrictions and vehicle restrictions along the interstate. The goal of this effort 

is to reduce accidents stemming from inclement weather on the state’s limited access highways.

System Components: Pennsylvania’s interstate system is divided into regional geographic 

sections so only impacted sections of the interstate system are restricted in response to various 

weather conditions. The system was designed to utilize the state’s existing and planned ITS 

infrastructure, meaning it was “no cost” to implement. When the system is activated, PennDOT 

utilizes variable message signs, highway advisory radio, 511, local media, Twitter and e-mail 

notification to inform the traveling public and commercial vehicle operators of the restrictions. 

PennDOT intends to expand its means of notification through the use of various social media in 

2012-13.

System Operations: The PennDOT Interstate Restriction system (Figure PA-1) consists of a 

managed plan to implement vehicle restrictions. The system is designed to increase and 

decrease restrictions as adverse weather conditions change. When certain weather conditions 

are reached, the first measure is triggered, warning motorists of winter road conditions. As 

conditions worsen, speed restrictions are imposed. Next, certain types of vehicles are barred 

from the interstate. If conditions are severe enough, eventually all interstate traffic is restricted. 

(In Figure PA-1, Note that “Normal Operations” implies routine snow removal operations. If a

restriction is not enacted, then standard snow removal operations continue. Also, the “Interstate 

Conditions” are defined as: 1 – clear; 2 – wet with freezing conditions; 3 – snow and/or slush 

covered; 4 – snow packed/significant snow cover; 5 – icy; 6 – impassable.)

During large-scale weather or “All-Hazard” emergencies, PennDOT operates under a uniform 

Incident Command System. The PennDOT Area Command center is located in the State 

Emergency Operations Center. Other representatives from impacted state agencies are also 

present. This coordination provides one location for coordinated incident response and 

planning between PennDOT, the Turnpike Commission, State Police, the National Guard and 

the State Emergency Management Agency. 

At the onset of an inclement weather event, PennDOT provides advanced warning of hazardous 

road conditions through variable message signs and highway advisory radio. PennDOT 

Engineering District Incident Command Centers coordinate with the Area Command as weather 

conditions deteriorate on reduced speed limits and restrictions in the impacted region. 

Engineering District Incident Command Centers review road conditions, weather forecasts and 

traffic volumes to determine if additional restrictions are necessary. Forecasts of high winds, 

icing or blizzard conditions prompt planning for vehicle type restrictions and can lead to total 

interstate closures. 
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Figure PA-1. Interstate restriction flow chart.

Transportation Outcome(s): Historically, adverse weather accidents on the interstate involve 

large commercial motor vehicles, requiring lengthy closure times given the weather conditions. 

Critical resources are diverted to detour efforts or providing safety for motorists in the resulting 

traffic queue. The Interstate Restriction system has dramatically reduced vehicle accidents 

during inclement weather events. PennDOT’s Traffic Engineering and Highway Safety Division 

performed an engineering study and confirmed that in winter storms of equal magnitude fewer 
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accidents occurred when 45 mph restrictions were in place. The reduction in accidents 

decreases traffic disruptions which allow PennDOT to efficiently continue maintenance 

operations on interstates. While the system was primarily developed for winter weather, speed 

limit reductions and specific commercial vehicle restrictions have been implemented 

successfully for high wind events like Hurricane Irene. 

Implementation Issues: The primary implementation issue is providing adequate notification of 

interstate restrictions to the motoring public and in-transit commercial motor vehicle operators. 

PennDOT continues to expand Intelligent Transportation System (ITS) infrastructure, 

coordination with surrounding states’ Traffic Management Centers, 511 systems, and the use of 

social media to provide interstate restriction notification to motorists. Also, when implementing 

commercial motor vehicle restrictions, concerns with commercial vehicle parking have been 

identified. PennDOT is developing global diversion routes to provide restricted traffic with 

alternate routes of travel around restricted corridors. PennDOT continues to work with the 

Pennsylvania Motor Truck Association to provide advanced warning of interstate restrictions to 

facilitate their members’ dispatch planning. 

Contact(s): 

• Charles C Goodhart - PennDOT, Director, Bureau of Maintenance and Operations, 717-

787-6899, cgoodhart@pa.gov

• Jason Norville - PennDOT, Section Chief, Winter Operations, 717-787-7004, 

janorville@pa.gov

• Jonathan Fleming - PennDOT, Section Chief, Emergency and Incident Management, 

717-772-1771, jonfleming@pa.gov

Reference(s):

• Goodhart, C., “Lessons Learned and Next Steps to Effective Winter Storm 

Management,”

http://www.nritsconference.org/downloads/Presentations10/C1_Goodhart.pdf, presented 

at the 2010 National Rural ITS Conference, August 2010 

Keywords: adverse weather, emergency management, weather information, speed limit 

restriction, incident management, traffic management, speed management, advisory speeds
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South Carolina DOT Hurricane Traffic Evacuation Operations

South Carolina has an extensive network of designated evacuation routes for motorists to use 

should there be a need to vacate coastal areas for a hurricane. There are twelve major 

evacuation routes, each approximately 100 miles long. From these twelve, one interstate and 

three primary routes can be reversed for higher evacuation traffic capacity leading away from 

the coast. All evacuation routes are “loaded” with vehicles from a designated area of the coast. 

Traffic is directed by signs and law enforcement to ensure maximum utilization of each route 

and to avoid over capacity of others. High coastal population numbers will present a capacity 

challenge to most routes used for evacuation. By aggressively managing traffic flow during 

evacuation, a higher probability of minimal drive times and reduced frustration for motorists will 

be realized. 

System Components: Intelligent Transportation System (ITS) elements play an integral role in 

the evacuation operations. All ITS infrastructure including Incident Responders, permanent and 

portable changeable message signs, traffic cameras, highway advisory radios, congestion 

sensing devices, and 511 Travel Info have been developed since Hurricane Floyd in 1999. The 

South Carolina Department of Transportation’s (SCDOT) traffic counters were in place prior to 

Hurricane Floyd and remain a valuable part of evacuation traffic evaluation today. Traffic 

camera video, congestion monitoring abilities, and traffic count data are used by the State 

Emergency Operations Center (SEOC) Emergency Traffic Management Unit to monitor and 

alter operations on evacuation routes as needed by the South Carolina Highway Patrol (SCHP) 

and SCDOT. The video viewed at the SEOC is fed through dedicated fiber optic cable from the 

State Traffic Management Center (STMC). This offers an extra measure of reliability and allows 

camera control of all SCDOT’s 302 video cameras statewide. A large number of these cameras 

are on coastal evacuation routes and are used daily to manage high traffic volumes in these 

areas. 

SCDOT’s Incident Responders, known as the State Highway Emergency Program (SHEP), are 

the other critical element of evacuation operations. During hurricane evacuation operations, they 

assist in keeping key evacuation routes in Myrtle Beach, Charleston, and Columbia free of 

incidents that lead to traffic congestion. SHEP units from northern areas of the state assist in 

covering the entire length of reversed Interstate 26 (I-26) from Charleston to Columbia (100 

miles) assisting to clear incidents that may impede traffic flow. Figure SC-1 is an aerial view of 

the termination of the evacuation reversal of I-26 near Columbia. 

System Operations: SCDOT and SCHP have adopted the Incident Command System (ICS) as 

the operational framework used for coastal evacuation. ICS will be used in all situations where 

Emergency Traffic Management is necessary throughout the state for adverse weather, manmade disasters, and so forth. ICS organization and concepts have been used successfully by 

fire services for decades and have proven themselves to be the best framework for all 

emergency services and disaster relief.

SCDOT and SCHP have jointly developed ICS Incident Action Plans (IAP) to address actions 

associated with each hurricane reversal route. IAPs have been developed for all evacuation 

activities along all coastal exit routes. Public response partners such as local law enforcement, 

fire services, emergency medical services, the law enforcement branch of the State Natural 

Resources Division, the State Law Enforcement Division (SLED), civil air patrol, National Guard, 

and county emergency management entities are incorporated in each IAP. This development 

effort has taken a substantial amount of detailed work by the parties involved. 
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The IAP concept has been tested through many Table Top Exercises (TTX) conducted with 

state and local partners and through a full-scale exercise last year for the simulated reversal of 

I-26 from Charleston to Columbia. The full-scale exercise entails bringing all assets, those of 

law enforcement and SCDOT traffic control devices, to each interchange on I-26 from 

Charleston to Columbia. The Interstate is not actually reversed but everything necessary to do 

so is at the roadside. The IAP concept is continuously exercised with the state’s annual fullscale simulation of the evacuation operation and the manning of evacuation traffic control 

points. During the exercise, simulated traffic problems will be presented to field personnel for 

mitigation by using IAP procedures identified through yearlong training. 

All evacuation routes are planned to 

provide lane continuity. For example, at 

major intersections or other transition 

points, two lanes will transition to two 

lanes and not be reduced to one. 

However, there are some exceptions as 

some roads are not wide enough to 

accommodate such continuity. There is 

extensive use of static traffic control 

devices (cones, barricades, etc.) and law 

enforcement personnel when a lane 

reversal is employed.

To aid in the goal of lane continuity, 

SCDOT has employed ITS technology to 

its maximum advantage along evacuation 

routes. Further SCDOT has instigated the 

use of ICS/IAP procedures to maximize 

operational efficiency and has assured 

sound, logical communications protocol 

during hurricane events. 

Transportation Outcome(s): The growing number of permanent residents within fifty miles of the 

coast and the high number of tourists that visit the coast each year during hurricane season 

motivate SCDOT to provide safe, effective evacuation operations. The coastal access road 

system has not kept pace with the population growth – only minor traffic capacity improvements 

have been made in the last forty-five years. This combination of constrained road system and 

high population makes it imperative that the maximum traffic capacity is achieved during 

evacuation events. 

The new ICS is paying many dividends in its simplicity, concise instruction and adaptive 

flexibility. Stakeholders and the public have realized the benefits accruing to them through this 

cooperative framework and periodic review process. The current initiative represents the state’s 

best efforts to protect the public when a hurricane threatens the coast. SCDOT is prepared for 

evacuations but will continue to evaluate yearly and improve as resources permit. 

Implementation Issues: Two implementation issues of the state’s evacuation plans are 

availability of evacuation routes and appropriate signage along those routes. The SCDOT and 

SCHP assess all routes in the field yearly to ensure evacuation signage is in place. Also, 

evacuation routes are altered if needed during the yearly assessment. 

Figure SC-1. Aerial view of I-26 near Columbia, 

SC where 100-mile evacuation reversal is 

terminated.
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Prior to hurricane season, meetings are held to reexamine emergency traffic flow procedures, 

confirm or alter staffing at traffic control points along the routes, and verify the ITS components 

used for hurricane evacuation traffic. These meetings occur in each of the state’s three major 

coastal evacuation areas with county emergency management officials, local law enforcement, 

SCDOT, SCHP Troopers, fire services, Emergency Management Services, and the National 

Guard in attendance. 

In 2012 the ICS/IAP concept for evacuation management was presented in the regional 

meetings with all partners. Additional meetings were held by SCDOT and SCHP to assure a 

familiarity amongst stakeholders during transition to the ISC approach. It is very important that 

all involved embrace ISC and understand their role in the IAP. 

Contact(s):

• Richard F. Jenkins, P.E., State Traffic Management, South Carolina Department of 

Transportation (SCDOT), 803-737-1454. jenkinsrf@scdot.org

• Captain Robert G. Woods, IV, MA, CPM, Emergency Traffic Management Unit, South 

Carolina Highway Patrol (SCDPS), 803-896-8722, rgwoods@schp.org

Reference(s):

• South Carolina Department of Transportation <http://www.scdot.org>

• South Carolina Emergency Management Division <http://www.scemd.org>

Keywords: Hurricane, emergency traffic management, Incident Command System (ICS), 

Incident Action Plan (IAP), Intelligent Transportation System (ITS), traveler information, 511, 

Incident Responders, emergency management, table top exercise, hurricane evacuation 

signing, highway capacity, hurricane evacuation studies, ingenuity
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South Dakota DOT Maintenance Decision Support System

Transportation agencies, which are responsible for providing safe, reliable highways throughout 

the winter season, face significant challenges:

• Travelers and commercial carriers with demanding delivery schedules expect higher 

levels of service.

• Transportation agencies have limited funding and staff.

• Reliable site- and time-specific reports of road conditions can be hard to get.

• Some weather conditions—particularly fog, frost, and blowing snow—can be difficult to 

forecast.

• Capabilities and limitations of new and innovative maintenance treatments are not fully 

understood.

• Agencies are losing their most seasoned maintenance workers, who have experienced 

diverse weather and treated a lot of roads during their careers.

• Transportation agencies face environmental challenges to the types and amounts of 

deicing materials they apply.

During the period of 2002–2012, the South Dakota Department of Transportation led a multistate pooled fund study that developed and extensively deployed a Maintenance Decision 

Support System (MDSS). The work is directed by a Technical Panel representing every 

participating state and the Federal Highway Administration and is administered by the South 

Dakota Department of Transportation’s Office of Research.

System Components: The premise behind MDSS is:

• if you know current road conditions;

• if you know the near- to medium-term weather 

forecast with confidence; 

• if you understand and can model the 

chemistry and physics of road surfaces 

subjected to weather, traffic, and maintenance 

activities; and

• if you know available maintenance 

resources—equipment, materials, operators, 

and time;

• then MDSS can recommend sound winter 

maintenance strategies—treatments, 

application rates and timing—and predict the 

resulting road conditions. By analyzing 

available alternatives, MDSS recommends 

most cost-effective treatments.

Major MDSS components include:

• a vendor supplied and operated information system that assimilates a wide variety of 

weather and maintenance data and models pavement surface response to weather, 

already applied maintenance treatments, and feasible future treatments;

Figure SD-1. Surface conditions 

predicted by MDSS closely match 

actual road conditions.
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• a desktop graphical user interface customized to individual users, providing detailed 

information on weather and road surface conditions and predictions, as well as 

maintenance treatment recommendations;

• on-vehicle systems data systems that inform the MDSS of weather conditions, road 

conditions, and applied maintenance treatments and then inform equipment operators of 

predicted conditions and maintenance recommendations.

System Operations: The MDSS incorporates the scientific framework and computational tools 

necessary to reliably recommend sound winter maintenance treatment strategies:

• Report Current Road Surface Conditions—MDSS accepts observations of current road 

conditions from manual observations, on-truck instrumentation, and in-pavement 

sensors. If no observations are available, MDSS estimates the condition of the road 

surface on the basis of recent weather and reported maintenance. 

• Report Actual Maintenance Treatments—Maintenance treatments (plowing and 

chemical application) are reported by manual entry or automatically by instrumented 

snowplows. 

• Assess Past and Present Weather Conditions—MDSS not only considers current 

weather conditions—such as temperature, dew point, wind velocity and direction, 

precipitation type and rate, presence of blowing and drifting snow, cloud cover, and 

visibility—but also past conditions recent enough to affect the road surface. 

• Assess Present Roadway State—MDSS’s physical and chemical models of the 

pavement and the “active layer”—the mix of water, ice, chemical, and grit—predict 

temperature, moisture type and depth, and chemical concentration.

• Predict Storm Event Weather— MDSS uses sophisticated ensembles of computer 

models, supplemented with input from live meteorologists, to make site- and timespecific weather predictions for four to six hours short-term, and up to twenty-four to 

thirty hours long-term.

• Identify Feasible Maintenance Treatments—MDSS recognizes the specific constraints in 

equipment, materials, operating hours, and crew size that exist at each road segment, 

and only considers maintenance treatments that fall within those constraints.

• Target Agency Priorities—MDSS considers the agency’s defined priorities regarding 

acceptable levels of service and the relative importance of a road segment compared to 

other segments.

• Predict Road Surface Behavior—Physical and chemical models in MDSS predict the 

future behavior of the active layer for each of the feasible maintenance treatments. For 

each treatment—chemical application, plowing, or a combination of both—the models 

predict whether the road will become dry, wet, snowy, or icy during the next several 

hours. MDSS can make predictions about numerous deicing materials, including liquids, 

brines, and salt mixtures.

• Communicate Recommendations to Supervisors and Workers—Finally, MDSS 

communicates treatment recommendations to truck operators or maintenance managers 

who direct fleet operations.

Transportation Outcome(s): Independent analysis of the benefits and costs of MDSS 

demonstrates potential for significant cost savings, improved service, or a combination of the 

two. A case study of New Hampshire’s five previous winters showed that, had MDSS been 

used, 23% less salt could have provided the same level of service; alternatively, the incidence 

of “unacceptable” driving conditions could have been reduced by 10-15% with equal salt use. In 

either case, the overall benefit/cost ratio was about 8:1. Similar case studies in Minnesota and 

Colorado showed smaller, but worthwhile, benefit/cost ratios.
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Indiana’s statewide deployment of MDSS during the winter of 2008-2009 provides the most 

direct evidence of MDSS benefit. Using MDSS as a management tool, Indiana reduced salt 

costs by $12 million and realized more than $1M savings in fuel and overtime. Even after 

normalizing for winter conditions, Indiana estimated overall savings at $11 million, 27% of its 

normal total winter budget.

In addition to cost efficiency, MDSS users have realized other intangible but important benefits:

• “one-stop” convenience for complete winter weather information;

• better anticipation of storm events and resulting road conditions;

• delivery of weather forecasts and maintenance recommendations directly to snowplow 

operators;

• more consistent and seamless winter maintenance among maintenance units;

• reduced environmental exposure to deicing chemicals;

• use of the MDSS storm playback feature as a powerful maintenance training and 

analysis tool.

Implementation Issues: States in the MDSS Pooled Fund Study have achieved varying levels of 

deployment. Some states, especially those that joined the study early, have deployed 

extensively throughout their state highway systems. Others that joined the study more recently 

have established limited or pilot deployments. Deployment issues common to the states have 

included:

• adoption of new computer and communications technology

• user acceptance of a new winter maintenance paradigm

• developing technical expertise to support and use the technology effectively

• financial investments needed to deploy and operate the MDSS.

Contact(s): 

• David L. Huft, Research Program Manager, 605-773-3358, dave.huft@state.sd.us

Reference(s): 

• MDSS Pooled Fund Study Fact Sheet: http://www.meridian-enviro.com/mdss/pfs/

• Tony McClellan, P.E., Paul Boone, P.E., and Melody A. Coleman, 2009. Indiana DOT 

Statewide Deployment Report. <http://www.meridianenviro.com/mdss/pfs/files/MDSSReportWinter08-09.pdf>

• Western Transportation Institute, Analysis of Maintenance Decision Support System 

(MDSS) Benefits & Costs, SDDOT Research Report SD2006-10-F, 2009.

<http://www.meridian-enviro.com/mdss/pfs/files/WTI-4W1408_Final_Report.pdf>

Keywords: Winter Maintenance Decision Support
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Figure TN-1. Fog detector.

Tennessee DOT Low Visibility Warning System

In December of 1973, the segment of Interstate 75 near Calhoun, Tennessee, was opened to 

traffic. Following this date, multiple vehicle accidents occurred due to visibility problems 

experienced in foggy conditions. The culmination of these events occurred on December 11, 

1990 when dense fog contributed to a series of chain-reaction collisions involving 99 vehicles 

with 42 injuries and 12 fatalities. In 1993, a fog detection and warning system was implemented 

along the Interstate section. This system includes a three-mile (five-kilometer) fog detection 

area spanning north and south of the Hiwassee River and an eight-mile (13-kilometer) warning 

zone on each approach to the fog prone area. In 2006, a project was initiated to upgrade the 

original system to current technology. Driver safety issues due to visibility problems have 

improved significantly since the system has been in place, with only one fog-contributed 

accident being recorded in 2001.

System Components: The fog detection component of the system is comprised of nine (9) 

forward-scatter visibility sensors (Figure TN-1), fourteen microwave radar vehicle detectors, and 

21 Closed Caption Television (CCTV) cameras (Figure TN-2). Data from these devices is 

transmitted by buried fiber optic cable to an on-site control center. Information from the on-site 

control center is relayed to a central computer located in the Highway Patrol office in Tiftonia, 

Tennessee, with the use of a leased point-to-point, T1 communication link. In addition to the 

electronic instrumentation, reflective roadside delineators are placed in the detection zone at 80-

foot increments for visibility estimation in the field.

The fog warning component of the system 

is made up of six (6) static warning signs 

with flashing beacons, ten Changeable 

Speed Limit Signs (CSLS) (Figure TN-3),

ten overhead Dynamic Message Signs 

(DMS), and two Highway Advisory Radio 

(HAR) transmitters. These warning systems 

are connected to the on-site control center 

by buried fiber optic cable, and to the 

central computer on the leased T1 

communication link. In addition to the 

warning systems, six remotely operated 

swing gates are located at interchange onramps to control access to the interstate in 

the most severe conditions (Figure TN-4). Figure TN-4. Swing gate.

Figure TN Figure TN-3. CSLS. -2. CCTV camera.
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System Operations: Operators monitor workstations connected to the system’s central 

computer from the Tennessee Highway Patrol Office in Tiftonia, Tennessee. This computer 

system processes information from the detectors and alerts operators when pre-defined visibility 

or traffic speed thresholds have been reached. When these conditions are met, operators 

trigger pre-programmed messages to be displayed on the DMS boards, and notify the Highway 

Patrol troopers in the field. Troopers are stationed in the fog zone area daily during the fog 

prone hours (from 5 AM to 10 AM). After receiving word from the operators, troopers move to 

verify the roadway conditions by counting the number of reflective roadside delineators visible. 

Table TN-1. Advisory and Control Strategies for Various Road Conditions.

Roadway Conditions Advisory & Control Strategies

OMS CSLS HAR

Case 1- Vehicle Speeds 

Below 45 mph

"CAUTION" alternating with "SLOW 

TRAFFIC AHEAD'' N/A N/A

Case 2 - Fog Detected 

With Visibility Greater 

Than 1,320 feet (402.3 

meters)

"CAUTION" alternating with "FOG 

AHEAD TURN ON LOW BEAMS"

"FOG" Displayed, & Flashing 

Warning Lights Activated N/A

Case 3 - Fog Detected 

With Visibility Between 480 

feet (146.3 meters) & 

1,340 feet (402.3 meters)

"FOG AHEAD" alternating with 

"ADVISORY RADIO TUNE TO XXXX 

AM"

"FOG" Displayed, Speed Limit 

Reduced To *50 mph, & 

Flashing Warning Lights

Activated

Activated

"FOG AHEAD" alternating with

"REDUCE SPEED TURN ON LOW

BEAMS"

"FOG" alternating with "SPEED LIMIT 

50 MPH"

Case 4 - Fog Detected 

With Visibility Between 240 

feet (73.2 meters) & 480 

feet (146.3 meters)

"FOG AHEAD" alternating with 

"ADVISORY RADIO TUNE TO XXXX 

AM"

"FOG" Displayed, Speed Limit 

Reduced To *35 mph, & 

Flashing Warning Lights 

Activated

Activated

"FOG AHEAD" alternating with 

"REDUCE SPEED TURN ON LOW 

BEAMS"

"FOG" alternating with "SPEED LIMIT 

35 MPH"

Case 5 - Fog Detected 

With Visibility Less than

240 feet (73.2 meters) 

"DETOUR AHEAD" alternating with 

"REDUCE SPEED MERGE RIGHT"

"FOG" Displayed & Flashing 

Warning Lights Activated Activated "1-75 CLOSED" alternating with 

"DETOUR"

"FOG AHEAD" alternating with 

"ADVISORY RADIO TUNE TO XXXX 

AM"

*The initial posted interstate speed limit on the roadway section Is 70 mph.

Currently, there are five separate cases in which fog warning and safety strategies are 

implemented. A decision is made as to what case is initiated based on the information provided 

by the system’s control software and field observations. Table TN-1 details the five cases and 

the corresponding advisory and control strategies. In Cases 3 through 5, there are three 
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separate messages for the DMS boards which appear relative to the sign’s location from the 

incident. The messages displayed in these three cases are dependent on the relative location 

and scale of the fog event. The DMS board located on the peripheral of the system will display 

the first alternating message. When closure of the interstate section is warranted (Case 5), the 

ramp gates are closed and a detailed route detour scheme is coordinated by the Tennessee 

Highway Patrol. The local media is contacted for all levels of activation. A pre-recorded 

message is broadcasted from the HAR (Highway Advisory Radio) when activated by the 

operators. The control software allows for customized message to be displayed and 

broadcasted. 

Transportation Outcome(s): From October 1st of 2011 to March 31th of 2012, the system 

detected fog in the target area a total of 45 times. This time frame represents the most active for 

fog production. Of the 45 times fog was detected by the sensors, advisory strategies were 

activated by the operators during 31 fog events. Of these events, 12 were elevated beyond the 

basic preliminary warning to a speed reduction. Since the system became operational, visibility 

conditions have warranted closure of the interstate section on two occasions: once for fog, and 

once for the presence of toxic smoke from a chemical plant fire. 

Driver safety issues due to visibility problems have improved significantly since the system has 

been in place, with only one fog-contributed accident being recorded, in 2001. There were no 

fatalities from this accident. The fog warning and detection system has the additional benefit of 

providing an effective tool for general incident management. In the October 2011 to March 2012 

time period, the system was manually activated to alert motorists of non-fog related incidents 34 

times. 

Implementation Issues: In the years leading up to the 1990 multi-vehicle incident, the 

Tennessee DOT and THP had implemented methodologies to help prevent fog-related 

accidents. In 1980, the DOT completed improvements that included enhanced striping, adding

raised pavement markers, adding flashing beacon warning signs, and providing portable detour 

signs for the THP. The 1990 accident spurred increased research, and the development of an 

interdepartmental plan of action. The existence of waste treatment facilities from a nearby paper 

plant necessitated studies into both the natural and man-made causes of fog production. After a 

review of available technology, it was decided that a fog detection and warning system should 

be implemented to augment safety practices carried out by the Tennessee Highway Patrol. 

The planning and design process of the system was aided by a review of a low visibility warning 

system located in Charleston, South Carolina. With defined requirements for the system 

functionality, the overall project area (based on fog incident information), and field component 

locations were selected. System redundancy was built-in to provide backup communication and 

power capabilities. The fog detection and warning system became operational in December of 

1993. 

In 2005, a determination was made that a renovation of the fog system was required. The 

various components that made up the system had aged to a point where it was difficult to 

continue operations and maintenance. A systems-engineering approach was used to ensure 

compatibility with future technologies and additions. Included in this upgrade was the integration 

of a CCTV video component. These cameras, mounted on 50-foot poles throughout the fog 

zone, are used to verify system operation and monitor weather and traffic conditions. 

The incorporation of the CCTV video required an improvement in the system’s communication 

abilities. The original system transmitted data with the use of a wireless radio microwave link. 

The required bandwidth for full-motion, real-time video and responsive remote camera operation 
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made the wireless system a less desirable design. The updated fog system operates with a 

leased, point-to-point, T1 communication link. In the future this T1 link will be replaced by a 

department-owned fiber optic link from the on-site control center to the Traffic Management 

Center (TMC) in Chattanooga, Tennessee. 

Contact(s):

• Brad Freeze, Tennessee DOT, ITS Design, 615-741-5017, Phillip.b.freeze@tn.gov

• Lt. Tommie Graham, Tennessee Department of Safety, 423-634-6898, 

Tommie.Graham@tn.gov

Reference(s):

• Dahlinger, D. “I-75 Fog Detection/Warning System Assessment, Field Review 

Summary”, June 2005.

• Dahlinger, D. and McCombs, B., “Fog Warning System Provides a Safety Net for 

Motorists,” Public Works, December 1995.

• National Transportation Safety Board (NTSB), “Multiple-Vehicle Collisions and Fire 

During Limited Visibility (Fog) on Interstate 75 near Calhoun, Tennessee, “Highway 

Accident Report NTSB No. HAR-92/02, NTIS No. PB92-916202, September 1992.

• Robinson, et al. “Safety Applications of ITS in Rural Areas: Section 3.2.8 Fog Detection 

Warning System – Tennessee”, EDL No. 13609, August 2002. 

Keywords: fog, visibility, low visibility warning system, freeway management, traffic

management, emergency management, law enforcement, advisory strategy, motorist warning 

system, traveler information, control strategy, speed management, access control, decision 

support, vehicle detection, environmental sensor station (ESS), variable speed limit (VSL), 

closed-circuit television (CCTV) cameras, dynamic message signs (DMS), highway advisory 

radio (HAR), gates, crashes, safety, Traffic Management Center (TMC)
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Texas DOT High Water Detection System

High water detection systems (HDWS) are installed in stream beds at road and stream crossing 

locations with a potential or a history of flooding. The Texas Department of Transportation 

(TxDOT) has installed twenty such of these systems throughout the San Antonio area. An 

additional six are being installed in 2012. The San Antonio district has installed one system in 

the metro area, while the other units (including the six new units under construction) have been 

installed in the rural areas surrounding San Antonio, primarily at locations in the Texas Hill 

Country, which are subject to flash flooding due to the region’s topography. The first units were 

installed in 2005. The unit cost is typically $75,000. 

System Components: The HWDS 

consists of the following elements:

• A stand pipe installed in the 

stream bed or measuring 

device attached to the crossing 

structure (bridge or culvert)

• Wire line or wireless 

communications from the 

measuring system to the local 

computer

• Wire line or wireless 

communications from the local 

computer to advanced warning 

signs

• Advanced warning signs, with 

flashers

• Central/Master software

• Cellular communications from the systems to a contracted operations center

• Internet-based communications from the contracted operations center to TxDOT’s 

network

• 

System Operations: The level of water in the stream bed is measured by a stand pipe or a 

device mounted on the bridge or culvert crossing the stream. The water level is transmitted to a 

local computer mounted in a cabinet near the stream crossing (which is installed above the 

flood elevation). The local computer activates flashers on warning signs on the approaches to 

the stream crossing. The local computer also transmits system status and water elevation to 

the central software application at the contracted operations center. Local topography for each 

location determined during installation and the water elevation data provided by the local 

computer are used to create a public Internet display, as seen in Figure TX-1, which provides a 

graphic display of the conditions. The conditions are noted as flooded or not flooded, or no 

data available. A secure web site is available for TxDOT staff that provides detailed information 

regarding each system’s status, operational history and historic water levels. 

•

Transportation Outcome(s): The San Antonio HWDS allow emergency responders, 

TransGuide Operators, TxDOT public information, the public and the media to monitor the 

conditions at the locations during a rain event. The flasher equipped advanced warning signs 

provide a notification to drivers that a road is flooded ahead. It allows maintenance crews to 

Figure TX-1. Public Internet display of TxDOTSan Antonio high water detection systems.
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monitor the HWDS from their offices and dispatch crews to set barricades when flood conditions 

are imminent.

Implementation Issues: The majority of TxDOT’s locations are in remote areas. Establishing 

communications to those sites required working with cellular providers, and identifying the best 

location for the equipment cabinet based on the topography and wireless coverage availability. 

All current TxDOT HWDS were installed by one manufacturer. The six new units are being 

installed by a second manufacturer. To ensure the data from the HWDS from any manufacturer 

is available, TxDOT required that the manufacturers provide the data using a specific protocol 

found in TxDOT’s Environmental Sensor Station documentation. That protocol is compliant with 

the National Transportation Communications for ITS Protocol (NTCIP). 

Contact(s): 

• Brian G. Fariello, P.E., Traffic Management Engineer, TxDOT-TransGuide, 210-731 

5247, brian.fariello@txdot.gov

Reference(s): 

• Texas DOT – San Antonio District Flood Station Map and Information webpage

<http://www.transguide.dot.state.tx.us/ITS_WEB/Frontend/default.html?r=SAT&p=San%

20Antonio&t=ess>

Keywords: TxDOT, TransGuide, Storm, Water, Detection, Pump, Flood, Stream
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Texas DOT Pump Station Monitoring System

The San Antonio District of the Texas Department of Transportation (TxDOT) installed 

monitoring systems in six storm water pump stations in locations where the roadway is below 

natural ground level. The pump stations are used to lift storm water to an elevation where the 

outflow can enter the gravity flow storm drainage system. The Monitoring Systems are used to 

determine the status of the pumps, determine the level of water in the wet wells, and provide an 

approximate time until the location floods. Before the monitoring systems were installed, 

maintenance crews had to visit each pump location during rain events to ascertain the status of 

the pumping equipment. The monitoring systems allow the maintenance crews to visit only the 

sites where maintenance issues and/or flood conditions require. The units were originally 

installed in 2000, but were recently upgraded at a cost of $13,000 each. 

System Components: The Pump Station 

Monitoring system consists of equipment 

located in the pump stations, 

communications to the TransGuide 

Operations Center, and an Internet 

display of the pump station data for 

TxDOT maintenance and operations 

staff. The equipment in the system 

includes the following elements:

• Field Computer 

• Remote terminal unit 

• Analog Input Module

• Pump Station Uninterruptible 

Power Supply (UPS)

• Internet Protocol (IP) Network 

Interface

• Central/Master Software

• Internet display

System Operations: The Pump Station Remote Terminal Units (PRTU) are connected to the 

sonic detector installed at the top of the wet well, which is used to determine the level of the 

water in the wet well. The sonic detector is connected to the pumps, and activates the pumps 

based on the water level. The PRTUs are connected to the pumps using contact closures, and 

determine when the pumps are in operation. The PRTUs transmit data from the pump stations 

to the TransGuide Operations Center. The pump station data is processed by the central 

software, and is available to TxDOT operations and maintenance staff using a non-public 

Internet display. The maintenance staff operations staff can dispatch technicians to repair failed 

pumps, or dispatch crews to set barricades if flooding of the roadway is imminent. Operations 

staff can place warning messages on Dynamic Message Signs, notify TxDOT public information 

staff and the media of flood conditions, and notify emergency services when flood conditions are 

present. 

Transportation Outcome(s): The San Antonio pump stations monitoring systems allow 

TransGuide operators to monitor pump operations during a storm incident and inform the public 

and response agencies should the pumps not be able to keep up with demand. It allows 

maintenance crews to monitor the pump stations equipment, dispatch repair technicians, and 

dispatch crews to set barricades when flood conditions are imminent. 

Figure TX-2. Storm water pump station: 

graphic image available to TxDOT operations 

and maintenance staff.
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Implementation Issues: Implementation of the pump station monitoring systems required that 

equipment from several manufacturers be interconnected. TxDOT was not aware of any prior 

applications where this equipment was used in this manner. The sonic detector had a standard 

data output port which was used as the basis of the system. Using the data output port, the 

detector provided the elevation of the water in the wet well. A remote terminal unit was 

identified that allowed for multiple contact closure connections (required for the pump status), in 

addition to receiving the elevation data from the sonic sensor. A software application was 

developed that included the central software and the software required for the computer in the 

remote terminal unit. The physical characteristics of the pump stations varied (engines, wet well 

diameter & height), and had to be researched for each pump station. The elevation of water in 

the wet well that would result in flooding of the roadway was initially estimated, and updated 

based on observed conditions following activation of the systems. 

Contact(s): 

• Brian G. Fariello, P.E., TxDOT-TransGuide, Traffic Management Engineer, 210-731-

5247, brian.fariello@txdot.gov

Reference(s): 

• Texas DOT – San Antonio District Flood Station Map and Information webpage

<http://www.transguide.dot.state.tx.us/ITS_WEB/Frontend/default.html?r=SAT&p=San%

20Antonio&t=ess>

Keywords: TxDOT, TransGuide, Storm, Water, Pump, Station, Detection
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Utah DOT Traveler Information Weather

The Utah Department of Transportation (UDOT) endeavors to provide timely, accurate and 

consistent weather-related traveler information so that travelers can make informed travel 

decisions. In response to this mission, UDOT has started the Traveler Information (TI) Weather 

program to provide the public with high quality road-specific forecasts before weather events,

and timely road condition observations during and after events. Through human-powered 

forecasting, condition reporting and partnering with other agencies, this program equips 

travelers with road weather information, helping them to make safe travel choices.

System Components: The TI Weather program consists of three contracted meteorologists 

located in UDOT’s Traffic Operations Center (TOC). TI meteorologists distribute working hours 

among themselves to fully cover hazardous weather events. They work alongside the TOC’s 

maintenance and operations weather forecasters (who are also contractors), but serve public 

motorists specifically. There are two products they provide to the public:

• Road weather impact forecasts 

• Road condition reports

These products are available on the UDOT Traffic website, smartphone app, Twitter account, 

and on the 511 phone line. 

TI meteorologists also provide customer service to public motorists with travel weather 

questions. Other duties include assisting with internal weather briefings for traffic operations 

personnel and compiling road weather data from each storm for post-event reviews. The 

program is joint-managed by the Weather 

Operations Manager and Traveler Information 

Manager.

System Operations: Road weather forecasts focus 

on expected travel impact resulting from upcoming 

weather. An example forecast graphic is shown 

here in Figure UT-1. These graphics accompany 

text forecasts and are posted as a Road Weather 

Alert on the UDOT Traffic website and app. Each 

segment of Utah’s state highways receives a 

manually-composed forecast, which provides 

details pertinent to travelers. The TI 

Meteorologists also record 511 messages which 

explain upcoming impacts in a way travelers can 

understand.

An important and unique aspect of pre-storm 

messaging is collaboration with the local National 

Weather Service (NWS) forecast office located in 

Salt Lake City. Forecasters from both agencies 

ensure the message is consistent between both 

agencies’ advisory products so that the public is 

not receiving conflicting forecasts from multiple 

agencies. NWS products are more visible by 

Figure UT-1. Weather impact graphic 

from March 1, 2012.
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media and public, and in this way, the message of travel impacts can reach a much larger 

audience than UDOT may be able to on its own.

Road condition reports are updated hourly from the TOC and at least twice daily from plow 

operators in the field. Plow operator reports are favored for their on-the-ground accuracy, but 

they lack the timeliness the public demands. Plow operations requires a high level of focus on 

safety and snow/ice mitigation, especially during hazardous and changing conditions, and 

reporting conditions becomes a lower priority. Utilizing in-field sensors, cameras, radar, 

forecasting models and direct communication with field personnel, the TI meteorologist 

populates these reports at a high frequency for UDOT’s TI outlets. UDOT also plans to initiate a 

citizen reporting program in the near future.

Transportation Outcome(s): The TI Weather program has improved UDOT’s level of service for 

public information. It has contributed to increased road weather awareness among media and 

public in Utah as they begin to understand the difference between “sensible” weather and road 

weather. For example, three inches of snow forecast to accumulate on grassy terrain may or 

may not translate to travel impacts, depending on road temperature, precipitation intensity, 

mitigation strategies, and so forth. It is assumed a road weather-savvy public will make more 

informed travel decisions before, during and after storms. Safer travel and increased road 

capacity during storms is an anticipated outcome. 

Communications technology has greatly increased the ability for information to be disseminated 

to the public in real-time, and as a result, UDOT’s road condition reports are more visible than 

prior technology would have enabled. Hourly updates satisfy a public need for this important 

safety information. 

At less than $140,000 per year, the cost of providing this service is relatively minimal for the 

important public service. UDOT has found that human-powered forecasts and road condition 

reports are produced at a much lower cost than running certain types of road weather models or 

relying strictly on automated field devices. Despite the low program cost, the forecasts are 

proven to be highly accurate, enabled in large part by human interaction in the forecast and 

observation processes. The TI meteorologists are removing some burden from the 

maintenance forecasters, who have been historically been limited to providing only a small 

component of public weather needs. This program has been very well received and supported 

in UDOT.

Implementation Issues: Basic software development was required to support the system. Local 

meteorologists with Bachelor’s degrees were recruited for the positions.

Contact(s): 

• Leigh Jones Sturges, Utah DOT Traffic Management Division, Weather Operations & 

RWIS Manager, 801-887-3735, leighsturges@utah.gov

• Lisa Miller, Utah DOT Traffic Management Division, Traveler Information Manager/PIO, 

801-887-3761, lisamiller@utah.gov

Reference(s): 

• TI Weather products available at <udottraffic.utah.gov/RoadWeatherForecast.aspx>

• Jones, L., G. Merrill, K. Barjenbruch, R. Graham, “Innovations in Impact-Based 

Wintertime Road Weather Warnings in Utah,” 1st Conference on Weather Warnings and 
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Communication, Oklahoma City, June 2011, available at

<http://ams.confex.com/ams/39BROADCAST/webprogram/Paper189115.html>

Keywords: traveler information, road weather, RWIS, forecast, 511, website, smartphone app
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Vermont Agency of Transportation: Transportation 

Operations Center

The Vermont Agency of Transportation (VTrans) Transportation Operations Center (TOC) is the 

focal point for VTrans’ Intelligent Transportation Systems (ITS) road weather management and 

traveler information systems operations. TOC staff are responsible for monitoring various ITS 

devices statewide, communicating with VTrans’ road crews, public safety (state and local), and 

emergency providers via radio and telephone, and updating the general and traveling public via 

Condition Acquisition Reporting System (CARS). TOC staff input information into CARS and 

CARS disseminates the information out to the public via 

511, Variable Message Signs (VMS), Low Power 

Frequency Modulation (LPFM) stations, web, e-mail, 

and text notifications.

System Components: The TOC consists of:

• Two Communications Specialists

• Internet Protocol (IP)-based Radio System that 

connects to all nine VTrans’ districts as well 

Vermont State Police Dispatch and local police.

• Video Wall for displaying data and video feeds 

from RWIS, local news, as well as different 

websites including 511.

System Operations: The TOC relies on various ITS 

devices such as RWIS, VMS, 511, and LPFM (LowPower FM).

The TOC has improved VTrans traveler information 

dissemination as well as winter road maintenance by 

providing VTrans’ maintenance crews with advanced 

weather information to allow crews to be proactive 

versus reactive to road and weather conditions 

throughout the state. This advanced weather 

information is ascertained by TOC crews monitoring 

National Oceanographic and Atmospheric Administration (NOAA), National Weather Service 

(NWS), as well as local radar to see what types of weather patterns are heading toward 

Vermont. In addition they provide RWIS data to Lyndon State College Meteorology Department

(LSC). LSC takes the data and inputs it into their computer models to analyze the data and 

provide accurate forecasts to the VTrans districts and 24 

to 48 hour advanced weather forecasts.

Transportation Outcome(s): The TOC, though small and 

undermanned, has provided a wealth of information to 

VTrans’ maintenance crews and the travelling public 

regarding adverse driving conditions during the winter, 

lane and road closures during road construction projects, 

and road closures due to crashes. VTrans’ maintenance 

crews heavily rely on feedback from TOC staff as they 

monitor RWIS data and camera images, NOAA, NWS, 

Figure VT-1. Traffic operations 

center.

 

Figure VT-2. Traffic operations 

center’s Gregory Fox, VTrans’ 

communications specialist.

Figure VT-3. Traffic operations 

center Mark Gerrish, VTrans’ 

fiber optic project manager.
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and local weather radar, etc. This gives the maintenance crews more time to plan on winter 

maintenance activities versus waiting for the event to happen and then having to react. Crews 

can have trucks loaded with correct materials (salt, sand, de-icing, etc.) and in some cases pretreat roads before winter events occur. The immediate benefit is less material wasted along 

with man-hours for having to return to the garage to change out materials due to changes in the 

weather patterns.

The travelling public and local media (TV and radio) have come to rely on 511 (both phone and 

web) and the various information disseminated. VTrans receives constant feedback (both 

positive and negative) from the public on how well the systems are working and how the 

information is used to make their travel more pleasant and feasible.

Implementation Issues: As with all new technology, implementation issues that have affected 

the TOC the most are reliability issues with ITS devices. VTrans relies heavily on the 

technology vendors to maintain and troubleshoot problems with the ITS devices. When an ITS 

device goes down, it may take the vendor a week or more to troubleshoot and fix. While the 

device is down, TOC staff cannot receive or review data from the device. This creates holes in 

the TOC staff’s ability to provide information to road crews and the travelling public.

As stated earlier, VTrans TOC is undermanned making it nearly impossible to provide up to date 

information at all times. To offset this, VTrans has looked at automating some features 

including allowing RWIS to control VMS in their vicinity and display pertinent messages related 

to the adverse weather conditions detected by the stations. However in order to do this, the 

RWIS and VMS must be reliable, i.e., on and in proper working condition. 

Another factor is communications. Because Vermont is such a rural state, Vermont is lacking in 

telecommunications infrastructure. This has also made it hard to implement ITS devices 

statewide and has thus further restricted the TOC’s “eyes and ears” as to what is happening 

(weather and road incidents) around the state.

Contact(s): 

• Robert T. White VTrans ConnectVermont ITS Administrator, 802-828-2781,

Robert.T.White@state.vt.us 

• Alec Portalupi VTrans Maintenance Engineer, 802-828-3889, Alec.Portalupi@state.vt.us

Reference(s): 

• State of Vermont 511 website <http://www.511vt.com>

• Vermont Agency of Transportation website <http://www.aot.state.vt.us/>

•

Keywords: Traffic Operations Center, road weather information systems
Best Practices for Road Weather Management

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Acronym List

AFWS Automated Flood Warning System

AASHTO American Association of State Highway and Transportation Officials

ATIS Advanced Traveler Information System

ATS Automated Transportation System

ATM Active Traffic Management

ATMS Advanced Traffic Management System

AVCS Advanced Vehicle Control System

AVL Automatic Vehicle Location

AWOS Automated Weather Observation Systems

B/C Benefit/Cost

BMP Best Management Practice

CARS Condition Acquisition Reporting System

CCTV Closed Circuit Television

CDPD Cellular Digital Packet Data

CHP California Highway Patrol

CMAQ Congestion Mitigation and Air Quality

CMS Changeable Message Signs

CSLS Changeable Speed Limit Signs

DCP Data Collection Platform

DCS Data Collection System

DMS Dynamic Message Sign

DOT Department of Transportation

DPS Department of Public Safety

DSL Digital Subscriber Line 

DSS Decision Support System

DUST Dual Use Safety Technology

EMS Extinguishable Message Signs

EOC Emergency Operations Center

ESS Environmental Sensor Station

EVMS Equipment Vehicle Management System

FDWS Fog Detection and Warning System

FIRST Freeway Incident Response Safety Team

FHWA Federal Highway Administration

FMS Freeway Management System

GIS Geographic Information System
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GOES Geostationary Operational Environmental Satellite

GPS Global Positioning System

HAR Highway Advisory Radio

HARS Highway Advisory Radio Service

HAZMAT Hazardous Material

HDWS High Water Detection Systems

HOT High Occupancy Toll

HOV High Occupancy Vehicle

IAP Incident Action Plan

ICS Incident Command System

ICWS Icy Curve Warning System

ILCS Intelligent Lane Control Signals

IP Internet Protocol

IRIS Intelligent Roadway Information System

ISP Information Service Provider

ITS Intelligent Transportation System

KHP Kansas Highway Patrol

KTA Kansas Turnpike Authority

LED Light Emitting Diode

LPFM Low Power Frequency Modulation

LSC Lyndon State College

MDC Mobile Data Collection

MDSS Maintenance Decision Support System

MMDI Metropolitan Model Deployment Initiative

MMS Maintenance Management System

MRC Measurement Research Corporation

MS/CVE Measurement Standards and Commercial Vehicle Enforcement

MVDS Microwave Vehicle Detection System

NCHRP National Cooperative Highway Research Program

NDFD National Digital Forecast Database

NOAA National Oceanographic and Atmospheric Administration

NTCIP National Transportation Communications for ITS Protocol

NWS National Weather Service

OFCM Office of the Federal Coordinator for Meteorology

OKFIRSTOklahoma’s First-response Information Resource System using 

Telecommunications

OLETS Oklahoma Law Enforcement Telecommunications System 
Best Practices for Road Weather Management

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PC Personal Computer

PLC Programmable Logic Controllers

PMR Performance Measurement and Reporting

PTR Pointer Record

PRTU Pump Station Remote Terminal Unit

PVC Polyvinyl Chloride

RPU Remote Processing Unit

RTMC Regional Traffic Management Center

RVD Radar Vehicle Detection

RWIS Road Weather Information System 

SCADA Supervisory Control and Data Acquisition

SCHP South Carolina Highway Patrol

SEOC State Emergency Operations Center

SHA State Highway Administration

SHEP State Highway Emergency Patrol

STC Smart Traffic Center

STMC State Traffic Management Center

TCC Traffic Control Center

TDP Temperature Data Probe

THP Tennessee Highway Patrol

TI Traveler Information

TMC Traffic Management Center

TP Tow Plow

TOC Traffic Operations Center

TRIS Transportation Research Information Services

TTX Table Top Exercises

UHF Ultra-High Frequency

UPS Uninterruptible Power Supply

US United States

USDOT United States Department of Transportation 

UTCS Uniform Traffic Control System

VDS Vehicle Detection Station

VHF Very High Frequency

VMS Variable Message Sign

VSL Variable Speed Limit

VSS Variable Speed Sign

WAN Wide Area Network
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U.S. Department of Transportation

Federal Highway Administration

Office of Operations

1200 New Jersey Avenue, SE

Washington, DC 20590

www.ops.fhwa.dot.gov

FHWA-HOP-12-046

June 2012