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U. S. Department Publication No. FHWA-NHI-04-160

of Transportation April 2004

**Federal Highway**

#### Administration

###### NHI Course No. XXXXXX

**Fundamentals of Road Weather Management**

######## 

## 

**Appendix C: Reference Manual**

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This document is not the complete reference guide but an excerpt from
the complete Fundamentals of Road Weather Management Reference Manual.
It covers the introduction, Chapter 4 (the chapter relating to the
material covered in the Participant Workbook), the summary and an
appendix.

Table of Contents

[Introduction 1](#introduction)

[Impact on Roadways & Travelers 1](#impact-on-roadways-travelers)

[Did you know? 1](#did-you-know)

[Mobility 1](#mobility)

[Urban Freeways 1](#urban-freeways)

[Rural Freeways 2](#rural-freeways)

[Chapter Four: 64](#chapter-four)

[Technological Resources 64](#technological-resources)

[The Benefits of Technology 64](#the-benefits-of-technology)

[History of Road Weather Information Systems (RWIS)
64](#history-of-road-weather-information-systems-rwis)

[1970s 64](#s)

[1980s 64](#s-1)

[Today 64](#today)

[Components of RWIS 65](#components-of-rwis)

[Environmental Sensor Stations (ESS)
65](#environmental-sensor-stations-ess)

[Processing Systems 66](#processing-systems)

[RPU 66](#rpu)

[CPU 66](#cpu)

[User Workstation 66](#user-workstation)

[Forecasts and Models 66](#forecasts-and-models)

[Benefits of Using RWIS 67](#benefits-of-using-rwis)

[Data Sharing Issues with RWIS 67](#data-sharing-issues-with-rwis)

[Ancillary Resources 68](#ancillary-resources)

[Thermal Mapping 68](#thermal-mapping)

[Thermal Mapping Success Story 68](#thermal-mapping-success-story)

[Satellite 69](#satellite)

[Mesonets 69](#mesonets)

[Did you know? 69](#did-you-know-1)

[Maintenance Decision Support System (MDSS)
70](#maintenance-decision-support-system-mdss)

[Information Dissemination 70](#information-dissemination)

[Kiosks 70](#kiosks)

[Warning Signs & Advisory Boards 70](#warning-signs-advisory-boards)

[Operations Centers 71](#operations-centers)

[511 & HAR 71](#har)

[Websites 71](#websites)

[Implementation 72](#implementation)

[Technical Challenges 72](#technical-challenges)

[Usage & Coordination 73](#usage-coordination)

[Universal Standards 74](#universal-standards)

[People Issues 74](#people-issues)

[The Change Factor 74](#the-change-factor)

[Delegation & Responsibility 75](#delegation-responsibility)

[Training 75](#training)

[Thresholds 75](#thresholds)

[Summary 76](#summary)

[Road Weather Management Resource 76](#road-weather-management-resource)

[An Understanding of Basic Meteorology
76](#an-understanding-of-basic-meteorology)

[Forecasting Services 76](#forecasting-services)

[RWIS and other Ancillary Resources
77](#rwis-and-other-ancillary-resources)

[Case Studies 77](#case-studies)

[Appendix A 212](#appendix-a)

[Case Studies: State Specific Matrix
212](#case-studies-state-specific-matrix)

# Introduction

Over the past 20 years, improvements have been made in the areas of road
sensors, anti-icing and information dissemination via tools such as Road
Weather Information Systems (RWIS.) However, concerns still remain
regarding uniform standards and data sharing. Ideally, all highway
personnel will be able to access open, tailored information about Road
Weather and act accordingly.

This reference manual provides you with key data on the basics of
meteology, weather services, technological resources, implementation
challenges and reference materials for the further research. There are
case studies at the end of the manual as well. These case studies serve
as a model of effective Road Weather solutions for various conditions
ranging from A -- (Avalanche) to W- (Wind).

## Impact on Roadways & Travelers

### Did you know?

> A one-day highway shutdown can cause anywhere from \$15 to \$76
> million in lost time, productivity and wages. -- *ITS Sheet,
> Publication No. FHWA-OP-01-012*

### Mobility

> Road weather conditions greatly affect the mobility of travelers.
> Snow, ice, slush, high winds and rain all contribute to reduced
> speeds, reduced highway capacity and road closures. This loss of
> mobility leads to additional lost time for travelers, and an increase
> in operating costs to clear and reopen roadways.
>
> To put into perspective, here are some key statistics, from the *FHWA
> Road Weather Management* office, on how mobility impacts travelers.

### Urban Freeways

-   Light rain -- speed reduction, 10%; capacity reduction, 4%

-   Heavy rain -- speed reduction, 16%; capacity reduction, 8%

-   Light snow -- capacity reduction, 5-10% depending on accumulation

```{=html}
<!-- -->
```
-   Heavy snow--speed reduction, nearly 38%; capacity reduction, 25-30%
    [^1]

### Rural Freeways 

-   Visibility below 530 ft -- Speed reduction, 13%; capacity reduction,
    approximately 6%.

-   Heavy precipitation and wet pavement -- speed reduction, 26%;
    capacity reduction, approximately 10%

# Chapter Four:

## Technological Resources

This chapter discusses the types of technology available for making road
weather decisions. The Road Weather Information Systems (RWIS) is
discussed is in detail as well as the challenges of implementing RWIS.
Other ancillary resources are also touched on.

## The Benefits of Technology

Technology is an invaluable tool in the road weather management process.
Advances in meteorological technologies provide better and more detailed
weather information. Road sensors, web-based information, satellite
images and mesonets all provide road weather data that enable better
decision-making. In this chapter, we will review some of the key
technological resources that support effective road weather management.

## History of Road Weather Information Systems (RWIS)

### 1970s

In the early 1970s, devices were tested to detect and monitor conditions
on bridge decks to aid in the timely treatment of localized icing
conditions resulting from frost. The first roadway installations proved
unsuccessful.

### 1980s

In the early 1980s, the detection and monitoring technology had advanced
to a point where it was tested in and then introduced to the general
highway environment to aid in the selection of appropriate snow and ice
control measures. In the late 1980s, the term RWIS was coined.

### Today

Today, RWIS refers to the entire spectrum of data collection, analysis,
dissemination, and display of road weather information. The systems have
come a long way from the early pavement sensors and now play a key role
in the success of road weather management programs across the country.

## Components of RWIS

RWIS are technological resources for gathering data on road conditions.
RWIS are made up of various components, including:

1.  A set of roadway atmospheric and pavement condition monitoring
    equipment, or sensors

2.  Data collection and distribution systems for measurements from the
    sensors.

3.  Equipment for the display and presentation of the measurements.

4.  Forecasts of weather and pavement conditions based partly on the
    measurements from the sensors and weather data available from
    sources including the National Weather Service (NWS), Value Added
    Meteorological Services (VAMS), various satellite broadcast systems;
    and the Internet.

## Environmental Sensor Stations (ESS)

The ESS are made up of sensors embedded directly in the pavement and
atmospheric sensors strategically positioned to measure changes in the
atmosphere. Each ESS is comprised of a suite of atmospheric and roadway
sensors, and a Remote Processing Unit (RPU). Each sensor station covers
a small segment of highway.

Today, there are about 1,200 RPUs in the U.S. There are about 4 million
route miles of public roads in the U.S., but only 662.000 miles are
under state administration. The National Highway System (NHS) consists
of only 160,000 route miles (mostly freeway and primary arterials), or
about 4% of the total, but carries 44% of all vehicle-miles traveled. If
one assumes that most of the ESS RPUs are on the NHS that means that
there is about one RPU per 133 route miles. This RPU spacing is
gradually being reduced each year with the installation of additional
ESS by highway DOTs.

The types of data collected by the sensors include:

+----------------------------------+-----------------------------------+
| -   Air Temperature              | -   Pavement Temperature          |
+----------------------------------+-----------------------------------+
| -   Amount, type and rate of     | -   The amount of chemical        |
|     precipitation                |     present on the roadway        |
+----------------------------------+-----------------------------------+
| -   Visibility                   | -   Surface condition             |
+----------------------------------+-----------------------------------+
| -   Humidity                     | -   Wind speed and direction      |
+----------------------------------+-----------------------------------+
| -   Dewpoint                     | -   Subsurface temperature        |
+----------------------------------+-----------------------------------+
| -   Freezing point of a brine on | -                                 |
|     the roadway                  |                                   |
+----------------------------------+-----------------------------------+

## Processing Systems

### RPU

RPUs located in the field gather data from the sensors and process the
data on site. They are designed to gather and store data at regular time
intervals and submit information collected. RPUs complete the following
steps:

1.  Gather data from sensors.

2.  Process Data.

3.  Determine significant changes.

4.  Store data in memory.

5.  Communicate and transfer data to the Central Processing Unit.

### CPU

CPUs or servers located in a centralized location at the agency or
contracting office receive data from RPUs in the field and disseminate
the information for end users. CPUs complete the following steps:

1.  Collect data from RPUs at predetermined frequency.

2.  Process the data.

3.  Store current and historical data.

4.  Transfer data to user workstations in various display formats.

### User Workstation

The individual user workstations receive information from the CPU or
server in text and high-resolution graphic format. Printers are
typically available for printing graphs and other charts in color.
Functions of the User Workstation include:

-   Display information received from CPU, once the CPU has processed
    the information, in text and graphic form.

-   Store historical data for extended periods.

-   Provide high-resolution color graphics.

-   Communicate externally via modem.

-   Connect to printer for text output and color graphic output.

-   Connect directly to CPU via RS-323 cable.

## Forecasts and Models

There are generally two types of tailored forecasts produced by RWIS.
One is a weather forecast and the other is a pavement temperature
forecast. The weather forecast is produced either by the ESS vendor or
by a VAMS using sensor data from the ESS. Pavement temperature forecasts
can be generated by a heat budget (balance) mathematical algorithm built
into the ESS/CPU capability, or by a VAMS using a preferred heat budget
mathematical model.

## Benefits of Using RWIS

RWIS can provide real-time, up-to-date, information on road conditions.
That information helps road weather management crews to effectively and
efficiently care for roadways and protect the safety of the traveling
public. Some of the benefits of using RWIS include:

-   Improved weather forecasts

-   Better prepared drivers

-   Reduced road patrols, labor and equipment hours

-   Lower snow and ice control, material, equipment hours

-   Increased efficiently or resource allocation during and adverse
    weather event

-   Increased cost-effectiveness of call-outs and overtime

-   Improved labor productivity and increased level of service

-   Increased efficiency of paving operations scheduling

-   Increased efficiency and cost-effectiveness of anti-icing[^2]^0^

## Data Sharing Issues with RWIS

The dissemination and sharing of data from RWIS systems can be
challenging. ESS, RPU and CPU equipment is purchased from a vendor,
sometimes with federal funds, by state and other highway agencies. These
facilities are operated and maintained by the agencies or, in some
cases, for them by a service vendor. This format initially led to
various problems, including:

-   The ESS system in one agency is not integrated with that of another
    agency

-   The data formats from the RPUs vary and might even be proprietary.
    Ownership of the data might reside in the state or it might reside
    in the vendors of the ESS. In some cases, the data are not available
    to third parties without special contractual arrangements. However,
    it should be noted that today new standard protocols and integration
    efforts are in place to ensure systems work together.

-   The quality of the data is not uniform because of varied calibration
    procedures and maintenance practices.

Some state DOTs, including Washington, Montana, Nevada and Iowa, have
developed web sites for the display of the data coming from the ESS. In
some cases, only portions of these web sites are available to the public
under restricted conditions, while other portions are password protected
for internal agency use. One of the issues is frequently the pavement
information. There is a movement by some state DOTs to share data from
their ESS with other state DOTs. However, this has been more the
exception than the rule and usually results from resource or budgetary
constraints. Liability issues and concerns also pose an institutional
barrier to the dissemination and sharing of ESS data.

## Ancillary Resources

Ancillary resources are additional tools available to road weather
management teams for making critical road weather decisions. The
availability of RWIS is limited and typically located on main highway
systems. However, local routes sometimes contain trouble spots that need
more attention during adverse weather conditions. Often these areas can
be addressed using alternative technological resources, such as thermal
mapping, satellite broadcast systems and mesonets.

## Thermal Mapping

Thermal mapping is the process of developing thermal profiles and other
climatological information for road surfaces. It involves making
measurements of pavement temperature, air temperature, relative humidity
and other climatological characteristics of the pavement environment.
The data are collected from instruments mounted on a special highway
vehicle driven over the roadway during various meteorological
conditions. These data are used to generate thermal "fingerprints" of
roadway surfaces.

Thermal mapping is useful in areas where anti-icing operations are often
conducted, areas where reduced chemical usage exists, and areas where a
number of different microclimates exist in a given area. Thermal mapping
can be used to document warm and cold highway spots, to help new staff
identify critical highway spots, to assist in forecasting pavement
temperatures between sites, to assist in setting RWIS locations, and to
support improved allocation of maintenance resources, including the
routing of crews, and balancing areas of responsibility to level work
load.

### Thermal Mapping Success Story

The Nevada DOT successfully used thermal mapping results to evaluate
recommended locations of ESS sites on the Nevada side of the Tahoe
Basin. A team consisting of a meteorologist, a snow and ice control
consultant, and NDOT field maintenance personnel had originally selected
the site locations. Based on thermal mapping results, a few of the ESS
sites were moved from the recommended locations to more pavement
temperature sensitive areas.

Thermal mapping results have also been used to develop pavement
temperature forecasts between the ESS sites. These forecasts are now
used by NDOT for decision-making in regards to anti-icing treatments,
specially during frost and black ice events. Finally, the pavement
temperature forecast information based on thermal mapping has been a
valuable teaching tool for new operators not familiar with the winter
microclimate conditions of the Tahoe Basin area.

## Satellite

For surface transportation professionals, the main impact from weather
satellites is the images that are shown on TV (such as the local news or
the Weather Channel). These give a broad view of the locations of
fronts, storms or areas of fair weather. Taking a progression of
pictures provides the ability to observe a storm system's movement
and/or evolution (growth or decay).

Satellite imagery is only one part of the arsenal needed to accurately
observe the weather on Earth. Satellites are combined with radar,
aircraft, ship, and surface observations, weather balloons, profilers,
etc, to get a picture of the current state of the atmosphere so that
predictions can be made.

## Mesonets

A mesonet is a set of weather observing stations, usually developed and
installed for a specific purpose. In a few states, mesonets are
collected centrally and made available to agencies or the public through
a web site. The web site can provide information for a wide geographical
area that might include data from ESS. The Utah Mesonet is one example.
The University of Utah's Cooperative Institute developed it for Regional
Prediction in cooperation with the Utah DOT, and NOAA including the NWS.
The Utah Mesonet relies on weather observing networks managed by
federal, state, and local agencies, and private firms. Support for the
Utah project is provided by the NWS and is used operationally by them to
monitor weather conditions around the region in order to protect lives
and property. The Mesonet is also used extensively by researchers to
understand severe weather events such as winter snow storms and damaging
winds."

### Did you know?

*Mesoscale is a size scale referring to weather systems smaller than
synoptic-scale systems, but larger than storm-scale systems. Horizontal
dimensions generally range from around 50 miles to several hundred
miles. Squall lines are an example of a mesoscale weather
system.*[^3]*^1^*

## Maintenance Decision Support System (MDSS)

The primary goal of a Decision Support System is to integrate weather,
road condition, and resource information in order to facilitate the
decision making process. The Maintenance Decision Support System, MDSS,
is an FHWA initiative to develop a decision support system for winter
road maintenance. While currently I a prototype stage, the MDSS will
enable state DOT's to view predicted weather conditions throughout the
state, become aware of the potential for deteriorating road conditions
before they occur, predict impacts of weather on road conditions, plan
treatment scenarios based on available resources, such as using
chemicals and plowing roads, and receive treatment recommendations based
on proven rules of practices.

The benefits of using the MDSS include reduced operating expenses, and a
higher level of service, which can result in safer and smoother highway
operations and traffic flow.

## Information Dissemination

Weather information collected from RWIS and other sources is also
disseminated to the public using a variety of available resources. The
following types of resources support the dissemination of weather
decisions to the public.

-   Kiosks

-   Warning signs, such as Variable Message Signs (VMS) & Advisory
    Boards

-   Operations Centers

-   511 & HAR

-   Traveler Websites

### Kiosks

Available in some state travel and tourist stops along major highways,
these kiosks provide motorists with road conditions for the roads they
are traveling.

### Warning Signs & Advisory Boards

Several state and turnpike highway agencies make excellent use of
warning signs, including VMS, and advisory boards. These signs are
strategically positioned along the roadside to warn motorists of road
surface conditions and the resulting road weather decisions.

For example, messages might include information on road closures,
reduced-visibility problems, icy bridge warnings, traction air
requirements, commercial traffic limitations, and special speed limit
requirements. Dynamic, as opposed to static warning messages have been
shown to be more effective in getting motorists attention to the
dangers. Static signs tend to always be there -- in fair or foul weather
-- and can become part of the roadway, not drawing attention. Examples
of automated input to VMS and advisory boards include:

-   Changeable speed limits in Nevada (an similar ongoing work in
    Arizona) using fuzzy logic algorithms based on ESS sensor input,

-   Icy road or bridge conditions in Minnesota at the entrance/exit to a
    tunnel

-   Bridge condition warning signs in Oregon.

### Operations Centers

State DOT traffic control and operations centers have been established
to accumulate data and information relative to road weather conditions.
These centers serve as a resource for maintenance decision-making.
Additionally, some state DOTs make road closure and condition reports
available to the public through the Internet. For example, take a look
at Arizona's Highway Closure and Restriction System Report
(<http://www.azfms.com/HCRSv2/arizona.html>).

### 511 & HAR

A new telephone hotline number where motorists can call to receive
updates on road weather conditions in the area where they are traveling.

### Websites

Several State DOT's provide detailed RWIS information on their websites
where the public can go and check several statistics for a given stretch
of road at a given time. Here are some examples of websites where you
can gather more information on weather.

-   Aurora --
    [http://www.aurora-program.org](http://www.aurora-program.org/)

-   Snow an Ice Pooled Fund Cooperative Programs (SICOP) -
    [http://www.sicop.net](http://www.sicop.net/)

-   FHWA - <http://www.ops.fhwa.dot.gov/weather>

-   NOAA --
    [http://www.iwin.nws.noaa.gov](http://www.iwin.nws.noaa.gov/)

-   IOWA DOT -
    [http://www.weatherview.dot.state.ia.us](http://www.weatherview.dot.state.ia.us/)

-   Arizona DOT - [http://www.azfms.com](http://www.azfms.com/)

-   Washington DOT Rweather Newsletter -
    <http://www.wsdot.wa.gov/eesc/atb/rwisnews/frames.html>

-   Foretell - <http://www.foretell.com/demo.htm>

-   Weather Channel - [http://www.weather.com](http://www.weather.com/)

-   Data Transmission Network - <http://dtnweather/wxweb/mainmenu.htm>

-   Advanced Regional Prediction System - <http://www.caps.ou.edu/ARPS>

-   Center for Analysis and Prediction of Storms -
    <http://www.caps.ou.edu/wx>

-   Surface Systems (fee based) -
    <http://www.truckerweather.com/index.asp>

-   Surface Systems (free) - <http://www.RoadWeather.com/>

## Implementation

### Technical Challenges

There are several issues associated with the **implementation** of an
RWIS network. Key RWIS implementation issues and some possible solutions
to these issues include:

Q: How many ESS are needed and how do we determine their locations?

A: This is best determined from inputs of various levels of use and
budget constraints. Where they should be located is best determined by
site surveys using a team consisting of a meteorologist, a snow and ice
control consultant, and local/district maintenance personnel.

Q: What are the power requirements for each ESS and what permits do we
need?

A: The power and permit requirements needed for each ESS are determined
initially during the site survey and refined later when the exact
locations are identified.

Q: What mode(s) of communication should be used to connect the ESS with

the CPU(s)

A: The mode of communication to be used to connect each ESS with the CPU
should be determined during the site survey data.

Q: Where is the CPU(s) or server physically to be located?

A: The CPU(s) or server should be physically located at central command
locations where decision-making takes place, or at a specified agency
internet or intranet hub location.

Q: How many workstations should have access to the CPU(s) or server and
what forms of communication should be used?

A: Major workstations should be located near the CPUs and connected by
hard wire communications. Management and budget constraints determine
how many PCs and laptops have access to the CPU. Server access could be
only limited by access to the Internet or agency intranet.

Q: What long and short-range weather forecast services do we need? Do we
need to hire a VAMS for site-specific weather and pavement temperature
forecasts?

> A: In general, it is advisable to hire a VAMS for site-specific
> weather and pavement temperature forecasts. The need for long and
> short-range weather forecast services depends on the decision-making
> requirements of the agency. The VAMS should be familiar with the
> site-specific and area meteorological and geographical constraints in
> order to provide valid and appropriate weather forecasts.

Q: Do we need or want a satellite broadcast system for up-to-date
weather information? Where should be receivers be located?

A: Management should determine the satellite broadcast system
requirements. If it is determined to be a need, the locations of the
receivers should be determined with significant input from field
maintenance engineers and supervisors.

Q: What data and information concerning road weather and road weather
decisions do we need to disseminate, and to whom?

A: The data and information you need to disseminate pertains to the
expected arrival time of the weather event, the nature and extent of the
weather event, and the expected conditions at the end of the event.
Individuals and agencies requiring this information depend on it for
making road weather decision.

### Usage & Coordination

Once you've established your RWIS needs and set up a system, there are
service usage and **coordination** issues to consider as well. Key RWIS
coordination issues include:

-   How will coordination and communication be handled between agency
    road weather decision makers and RWIS service providers, such as ESS
    maintainers, NWS, VAMS, satellite broadcast weather information,
    etc.,?

-   How and when will road weather decisions be disseminated to:

    -   Highway maintainers?

    -   Traffic managers?

    -   Emergency managers?

    -   Safety engineers?

-   How and when will updates on road weather conditions be disseminated
    to various other agencies and groups of individuals?

### Universal Standards

The procurement specifications for new RWIS equipment should require
that the system be compliant with the ESS National Transportation
Communications for ITS Protocol (NTCIP). The NTCIP is a joint
standardization project of the American Association of State Highway and
Transportation Officials (AASHTO), the Institute of Transportation
Engineers (ITE), and the National Emergency Management Association
(NEMA), with funding from the Federal Highway Administration (FHWA).

NTCIP is the generic name for the set of standards that define how
roadside services talk to a central system. In the case of RWIS, there
is a specific set of standards defining how the TPU of an ESS
communicates with the CPU at a control center. The first version of this
set of standards was completed in 1996-1998 and man highway agencies are
successfully deploying field units that conform to this standard. Work
on the 2^nd^ version of the standards has begun and will add features,
such as the capability to control automated pavement spray systems for
remote anti-icing operations.

RWIS communications standards and standardized testing methodologies for
pavement sensors are just a few of the projects completed by the Aurora
consortium. These and other completed projects plus those currently
underway within Aurora can be found on the Aurora website
([http://www.aurora-program.org](http://www.aurora-program.org/)).

Finally, ENTERPRISE (a pool-fund organization consisting of seven U.S.
state DOT's, Canada, and the Netherlands) has developed a set of test
procedures, which have been automated in "Trevilon Ntester" software.
This software is available for free download from Trevilon's website
([http://www.trevilon.com](http://www.trevilon.com/).)

## People Issues

### The Change Factor

One of the biggest challenges in implementing any new technology is
winning over the people who will use it. We all know the saying "changes
is good" but more often than not we resist it when it comes to our own
work. People have a way of doing things and don't want to change. In
general, human beings tend to resist change, specially, when it is
connected with new technology that appears to challenge their old ways
of doing business. However, we can no longer afford to be reactive in
making road weather decisions. We must be proactive in order to "stay
ahead of the storm," and RWIS technology is a valuable took in making
proactive road weather decisions. Technological change in the handling
of road weather issues is needed and as a result the culture must shift
as well. Highway crews and management teams must get on board and start
the culture change for proactive decision-making and tools such as RWIS
to succeed.

### Delegation & Responsibility

Another people issue associated with implementing road weather
technologies deals with the establishment of responsibilities, the
delegation of authority, and the implementation of policies. Some of the
questions that need addressing include:

-   Who or what group will be responsible for maintaining the RWIS
    network including calibration of the sensors?

-   Who or what group will be responsible for monitoring the output from
    the ESS along with the weather status and weather forecast
    information?

-   Who or what group will be responsible for making road weather
    deacons?

Establishing roles and responsibilities enables an agency to take the
information provided by RWIS and use it effectively. The information is
only valuable in the hands of the right people to make the right
decisions.

### Training

Training, as with any new technology is critical to the successful
implementation of RWIS and other technological resources. When
considering training, keep the 5 W&H rule in mind

-   Who needs to be trained?

-   What do individuals need to know in order to successfully complete
    their work using technology?

-   What training programs are available?

-   Where will training take place? And when?

-   Why is a technological resource in use? How will it helps everyone
    in their individual job roles?

## Thresholds

Threshold limitations, such as location, budget, and physics impact the
implementation of any new road weather technology. For example, budget
constraints might impose limitations to the TWIS network size, and
expandability.

Or, you might need to consider the physics governing the formation of
frost or localized icing on bridge decks when deciding what type and
location of sensors should be used for ESS in connection with bridge
deck icing problems.

Or, there might be location constraints that prevent the placement of an
ESS in an ideal location, e.g., terrain issues, right-of-way
limitations, limited access to power, or limited communication
reception.

# Summary

## Road Weather Management Resource

-   Basic Meteorology.

-   Forecasting Services

-   RWIS and other ancillary resources

-   Case Studies

Road weather maintenance issues affect all areas of the transportation
industry, including the highway crews, traffic managers, emergency
managers, safety engineers and motorists who travel out nations'
roadways. By understanding, first the road weather problem, and second
the resources available, transportation professionals can and do make an
impact on the successful management of the road weather problem.

### An Understanding of Basic Meteorology

The Basics of Meteorology are important for all transportation
professionals to know because they provide a basis for understanding
weather forecasts, and other weather services. For example, without an
understanding of the difference between frost and freezing rain, the
proper decisions cannot be made and the information provided in a
forecast cannot be effectively utilized. The basics of meteorology are
detailed in Chapter Two: Meteorology and the Non-Meteorologist, and
include:

-   A weather glossary of basic terms.

-   Weather variables that affect road conditions.

-   Basic definitions of the various types of weather services.

### Forecasting Services

Tailored weather forecasts are an essential tool for handling road
weather problems. They provide detailed forecast data on specific sites,
per the specifications, requirements and needs of the particular agency.
Some of these services do charge fees for their services; however, the
fees typically balance out with the cost saving of more efficient
handling of road weather issues. Ultimately, the goal of tailored
weather services is to provide the information necessary for agencies to
be proactive. The types of weather services, as well as the benefits of
each are covered in Chapter Three: Tailored Weather Services. Services
covered include:

-   National Weather Service (NWS)

-   Media Weather Services

-   Consulting Meteorological Services

-   Value Added Meteorological Services (VAMS)

### RWIS and other Ancillary Resources

Technology is a valuable resource in proactive planning and efficient
road weather management. The advances in technology now make it easier
to collect real time data on the road conditions, pavement temperature,
air temperature and visuals and multiple locations. The combination of
technology of technology and meteorology has also successfully resulted
in the RWIS system, available to all states and effectively used in
several areas, particularly those with adverse winter weather issues.
The types of technology available and the implementation issues with
them are covered in Chapter Four: Technology: Resources and
Implementation. Resources covered include:

-   Road Weather Information Systems (RWIS)

-   Thermal Mapping

-   Satellites

-   Mesonets

-   Warning Signs and Advisory Boards

-   Operations Centers

### Case Studies

Case Studies provide an opportunity to examine how things have worked in
the past, both successes and failures. They show resources and knowledge
in use and provide concrete data on cost savings, reductions in
accidents or risk of accidents, chemical usage and much more. Based on
the type of road weather conditions you are researching, the case
studies provided herein are organized by type of weather, then the
problems that type of weather can produce.

# Appendix A

## Case Studies: State Specific Matrix

+------+------------------+------+-------+---------------+------------+
| **   | **Weather        | **Lo | #     | **Solution**  | **Cor      |
| Type | Problem**        | cati | ####  |               | responding |
| of   |                  | on** |       |               | Case       |
| W    |                  |      | #     |               | Study**    |
| eath |                  |      | ####  |               |            |
| er** |                  |      | Profe |               |            |
|      |                  |      | ssion |               |            |
+------+------------------+------+-------+---------------+------------+
| Snow | Forecast for an  | Iowa | M     | Review        | IDOT       |
|      | accumulation     |      | ainte | pavement      | M          |
|      | greater than the |      | nance | temperature   | aintenance |
|      | adopted level of |      |       | forecast.     | Management |
|      | service, is      |      |       |               | S          |
|      | expected to      |      |       | Notify crews  | ystem/snow |
|      | occur after      |      |       | to assemble 2 | removal    |
|      | normal duty      |      |       | hours before  | plan.      |
|      | hours.           |      |       | forecast      |            |
|      |                  |      |       | onset time    |            |
|      |                  |      |       | (if actual    |            |
|      |                  |      |       | accumulation  |            |
|      |                  |      |       | likely).      |            |
+------+------------------+------+-------+---------------+------------+
| Snow | Forecast for     | Wi   | Tr    | Review of     | WisDOT     |
|      | snow showers in  | scon | affic | pavement      | Traffic    |
|      | Dane County      | sin- | Manag | temperatures  | Operations |
|      | during morning   | Dane | ement | current and   | Plan       |
|      | commute hours.   | Co   |       | forecast      |            |
|      |                  | unty |       | reveals above |            |
|      |                  |      |       | freezing      |            |
|      |                  |      |       | throughout    |            |
|      |                  |      |       | period:       |            |
|      |                  |      |       |               |            |
|      |                  |      |       | Alert Dane    |            |
|      |                  |      |       | County Road   |            |
|      |                  |      |       | Maintenance   |            |
|      |                  |      |       | (responsible  |            |
|      |                  |      |       | for S&IC).    |            |
|      |                  |      |       |               |            |
|      |                  |      |       | Re            |            |
|      |                  |      |       | commendation: |            |
|      |                  |      |       | Do Nothing.   |            |
+------+------------------+------+-------+---------------+------------+
| S    | Sleet            | Wes  | M     | Undertake     | PennDOT    |
| leet | unexpectedly     | tern | ainte | anti-icing.   | M          |
|      | occurring and    | Penn | nance |               | aintenance |
|      | not forecasted.  | sylv |       |               | Management |
|      |                  | ania |       |               | System,    |
|      | Forecast calls   |      |       |               | S&IC Plan  |
|      | for decreasing   |      |       |               |            |
|      | air              |      |       |               |            |
|      | temperatures.    |      |       |               |            |
|      |                  |      |       |               |            |
|      | Pavement sensors |      |       |               |            |
|      | indicate already |      |       |               |            |
|      | freezing         |      |       |               |            |
|      | pavements, and   |      |       |               |            |
|      | no chemical      |      |       |               |            |
|      | present.         |      |       |               |            |
+------+------------------+------+-------+---------------+------------+
| S    | Sleet is         | New  | Tr    | Issue news    | T          |
| leet | forecast for the | York | affic | bulletins for | ri-borough |
|      | P.M. commute.    | City | Manag | expected      | and        |
|      |                  | -New | ement | reduced       | bi-state   |
|      | Pavement         | Je   |       | visibility,   | traffic    |
|      | temperature      | rsey |       | and           | operations |
|      | forecast is for  |      |       | associated    | plans.     |
|      | above freezing   |      |       | delays.       |            |
|      | level.           |      |       |               |            |
|      |                  |      |       | TOC           |            |
|      |                  |      |       | undertakes    |            |
|      |                  |      |       | increased     |            |
|      |                  |      |       | surveillance  |            |
|      |                  |      |       | of exposed    |            |
|      |                  |      |       | locations     |            |
|      |                  |      |       | such as major |            |
|      |                  |      |       | bridges.      |            |
+------+------------------+------+-------+---------------+------------+
| Free | Forecast is      | Miss | M     | Undertake     | MODOT and  |
| zing | calling for      | ouri | ainte | anti-icing.   | City       |
| rain | freezing rain    | --   | nance |               | M          |
|      | overnight,       | St.  |       | Monitor       | aintenance |
|      | without          | L    | Emer  | anti-icing    | Management |
|      | preceding        | ouis | gency | progress and  | Systems    |
|      | precipitation.   |      | Manag | results as    |            |
|      | Pavements        |      | ement | input to      | City and   |
|      | currently above  |      |       | selecting     | County of  |
|      | freezing, but    |      |       | best routes   | St. Louis  |
|      | forecast to fall |      |       | for response  | emergency  |
|      | to 30^0^ F       |      |       | and delivery  | Response   |
|      | during clear     |      |       | to emergency  | Plan.      |
|      | skies of early   |      |       | rooms.        |            |
|      | evening.         |      |       |               |            |
+------+------------------+------+-------+---------------+------------+
| **   | #######          | **Lo | #     | **Solution**  | **Cor      |
| Type |  Weather Problem | cati | ####  |               | responding |
| of   |                  | on** |       |               | Case       |
| W    |                  |      | #     |               | Study**    |
| eath |                  |      | ####  |               |            |
| er** |                  |      | Profe |               |            |
|      |                  |      | ssion |               |            |
+------+------------------+------+-------+---------------+------------+
| Free | Currently it is  | Or   | M     | Monitor RWIS  | ODOT       |
| zing | raining, with a  | egon | ainte | and NWS       | Maint.     |
| rain | forecast of      | Wa   | nance | reports       | Mgmt.      |
|      | turning to       | shin |       | closely.      | System,    |
|      | freezing rain 3  | gton | Tr    |               | S&IC       |
|      | hours from now,  |      | affic | Undertake     | element.   |
|      | and then to snow | Colu |       | anti-icing at |            |
|      | 3 hours after    | mbia |       | outset of     |            |
|      | that, as air     | Gorg |       | freezing      |            |
|      | temperatures     | e/Po |       | rain.         |            |
|      | drop to 25^o^ F. | rtla |       |               |            |
|      | Pavement         | nd - |       | Announce      |            |
|      | temperature      | V    |       | Imminent      |            |
|      | forecast to drop | anco |       |               |            |
|      | below freezing   | uver |       |               |            |
|      | one hour after   |      |       |               |            |
|      | snowfall starts. |      |       |               |            |
|      | Freezing rain    |      |       |               |            |
|      | just started at  |      |       |               |            |
|      | The Dalles,      |      |       |               |            |
|      | confirming the   |      |       |               |            |
|      | forecast.        |      |       |               |            |
+------+------------------+------+-------+---------------+------------+
| F    | Dewpoint         | I    | M     | Undertake     | IDOT       |
| rost |                  | owa- | ainte | anti-icing,   | Winter     |
|      | Dewpoint         | Iowa | nance | bridges and   | M          |
|      | approaching      | City |       | approaches    | aintenance |
|      | pavement         |      |       | first.        | Manual     |
|      | temperature at   |      |       |               |            |
|      | 32^o^ as         |      |       |               |            |
|      | identified by    |      |       |               |            |
|      | monitoring RWIS  |      |       |               |            |
|      | ESS output.      |      |       |               |            |
|      | Frost forecast   |      |       |               |            |
|      | to occur on      |      |       |               |            |
|      | bridges and      |      |       |               |            |
|      | approaches in    |      |       |               |            |
|      | two hours.       |      |       |               |            |
+------+------------------+------+-------+---------------+------------+
| B    | At elevations    | Or   | M     | Apply liquid  | Manual of  |
| lack | above 1500 feet, | egon | ainte | or pre-wetted | Practice   |
| Ice  | pavement         | co   | nance | solid         | of an      |
|      | temperature is   | stal |       | chemical;     | Effective  |
|      | dropping below   | m    |       | reapply if    | Anti-icing |
|      | freezing and dew | ount |       | pavement      | Program    |
|      | point            | ains |       | becomes wet   |            |
|      | temperature is   |      |       | or thin ice   |            |
|      | 32^o^ F to 34^o^ |      |       | again forms.  |            |
|      | F. Black ice has |      |       |               |            |
|      | been observed,   |      |       |               |            |
|      | but the pavement |      |       |               |            |
|      | can still be     |      |       |               |            |
|      | seen.            |      |       |               |            |
+------+------------------+------+-------+---------------+------------+
| A    | Following        | Al   | Main  | Undertake     | ADOT&PF    |
| vala | several days of  | aska | tenan | preparations  | Avalanche  |
| nche | rain, heavy      | Se   | ce/Tr | for avalanche | Plan       |
|      | snowfall is      | ward | affic | control, and  |            |
|      | forecast with    | Hig  | Manag | road closures |            |
|      | air temperatures | hway | ement | at Bird       |            |
|      | below 20^o^ F    |      |       |               |            |
|      | and east winds   |      | Emer  | Notify        |            |
|      | 50 mph at source |      | gency | responders of |            |
|      | regions, Portage |      | Manag | imminent      |            |
|      | to Potter.       |      | ement | closures,     |            |
|      |                  |      |       | ambulances    |            |
|      |                  |      |       | south of      |            |
|      |                  |      |       | closures go   |            |
|      |                  |      |       | to Seward.    |            |
|      |                  |      |       | Place         |            |
|      |                  |      |       | helicopter    |            |
|      |                  |      |       | responders on |            |
|      |                  |      |       | standby.      |            |
+------+------------------+------+-------+---------------+------------+
| A    | Forecast of      | Wa   | M     | Prepare for   | WSDOT      |
| vala | heavy snowfall   | shin | ainte | avalanche     | Maint.     |
| nche | and strong       | gton | nance | control       | Mgmt.      |
|      | southerly winds  | S    |       | operations at | System,    |
|      | following a week | tate | Tr    | chronic slide | S&IC       |
|      | of windy, dry    | R    | affic | region just   | /Avalanche |
|      | conditions in    | oute | Manag | west of the   | element.   |
|      | which avalanche  | 2    | ement | Pass.         |            |
|      | source regions   | near |       |               | WSDOT      |
|      | have become      | Ste  | Emer  | Provide       | Traffic    |
|      | consolidated and | vens | gency | public        | and        |
|      | icy.             | Pass | Manag | advisory via  | Weather    |
|      |                  |      | ement | media outlets | info on    |
|      |                  |      |       | and WSDOT web | Internet   |
|      |                  |      |       | site, calling |            |
|      |                  |      |       | attention to  |            |
|      |                  |      |       | info          |            |
|      |                  |      |       | available at  |            |
|      |                  |      |       | [ht           |            |
|      |                  |      |       | tp://www.atmo |            |
|      |                  |      |       | s.wa.shigton. |            |
|      |                  |      |       | edu](http://w |            |
|      |                  |      |       | ww.atmos.wa.s |            |
|      |                  |      |       | higton.edu/). |            |
|      |                  |      |       |               |            |
|      |                  |      |       | Standby for   |            |
|      |                  |      |       | trouble.      |            |
+------+------------------+------+-------+---------------+------------+
| Red  | Conditions       | T    | Tr    | Advise        | Tennessee  |
| uced | conductive to    | enne | affic | motorists via | Fog        |
| vi   | fog formation    | ssee | Manag | flashing      | Detection  |
| sibi | detected by the  | --   | ement | beacons, HAR, | and        |
| lity | Tennessee Fog    | T    |       | variable      | Warning    |
|      | Detection and    | enne |       | speed limit   | System     |
|      | Warning System   | ssee |       | signing,      |            |
|      | for the area 8   | R    |       | control       |            |
|      | miles either     | iver |       | access.       |            |
|      | side of the      | Va   |       |               |            |
|      | Hiwassee River.  | lley |       |               |            |
+------+------------------+------+-------+---------------+------------+
| **   | #######          | **Lo | #     | **Solution**  | **Cor      |
| Type |  Weather Problem | cati | ####  |               | responding |
| of   |                  | on** |       |               | Case       |
| W    |                  |      | #     |               | Study**    |
| eath |                  |      | ####  |               |            |
| er** |                  |      | Profe |               |            |
|      |                  |      | ssion |               |            |
+------+------------------+------+-------+---------------+------------+
| Red  | Tule fog is      | Ca   | Tr    | VMS and       | Plan       |
| uced | forming,         | lifo | affic | Caltrans      |            |
|      | expected to be   | rnia | Manag | computerized  |            |
| Vi   | persistent.      | --   | ement | fog warning   |            |
| sibi |                  | San  |       | signs on I-5; |            |
| lity |                  | Joa  |       | and advise    |            |
|      |                  | quin |       | widely via    |            |
|      |                  | R    |       | local media   |            |
|      |                  | iver |       | outlets.      |            |
|      |                  | Va   |       |               |            |
|      |                  | lley |       | Increase      |            |
|      |                  |      |       | surveillance  |            |
|      |                  |      |       | on Veterans   |            |
|      |                  |      |       | Memorial      |            |
|      |                  |      |       | Bridge.       |            |
|      |                  |      |       |               |            |
|      |                  |      |       | Initiate Pace |            |
|      |                  |      |       | Program with  |            |
|      |                  |      |       | California    |            |
|      |                  |      |       | Highway       |            |
|      |                  |      |       | Patrol        |            |
|      |                  |      |       | entering and  |            |
|      |                  |      |       | slowing       |            |
|      |                  |      |       | traffic       |            |
|      |                  |      |       | stream.       |            |
+------+------------------+------+-------+---------------+------------+
| Rain | Flooding         | T    | Tr    | Flashing      | City of    |
|      |                  | exas | affic | warning signs | Dallas,    |
|      |                  |      | Manag | to alert      | Texas      |
|      |                  |      | ement | motorists to  | Flood      |
|      |                  |      |       | high water    | Warning    |
|      |                  |      |       | conditions    | System.    |
|      |                  |      |       | ahead         |            |
+------+------------------+------+-------+---------------+------------+
| Rain | Forecast of      | Wes  | M     | Cancel        | MDOT       |
|      | unseasonably     | tern | ainte | scheduled     | Maint.     |
|      | 3-day period of  | Mon  | nance | pavement      | Mgmt.      |
|      | rain (July)      | tana |       | marking       | System     |
|      |                  |      |       | activities:   |            |
|      |                  |      |       | schedule      |            |
|      |                  |      |       | other         |            |
|      |                  |      |       | maintenance   |            |
|      |                  |      |       | activities    |            |
|      |                  |      |       | instead.      |            |
+------+------------------+------+-------+---------------+------------+
| High | Northerly winds  | Wa   | M     | Monitor       | WSDOT      |
| w    | of greater than  | shin | ainte | actual wind   | Traffic    |
| inds | 60 mph are       | gton | nance | speeds and    | Operations |
|      | forecast for     | --   |       | wave          | Plan       |
|      | western          | Floa | Tr    | conditions by |            |
|      | Washington,      | ting | affic | wind sensors  |            |
|      | which will cause | Bri  | Manag | and cameras   |            |
|      | wave overtopping | dges | ement | on floating   |            |
|      | of bridge        |      |       | bridges.      |            |
|      | roadways.        |      |       | Consider      |            |
|      |                  |      |       | bridge        |            |
|      |                  |      |       | openings, if  |            |
|      |                  |      |       | necessary, to |            |
|      |                  |      |       | reduce stress |            |
|      |                  |      |       |               |            |
|      |                  |      |       | Alert public  |            |
|      |                  |      |       | to prospect   |            |
|      |                  |      |       | for bridge    |            |
|      |                  |      |       | closures due  |            |
|      |                  |      |       | to wave       |            |
|      |                  |      |       | overtopping   |            |
|      |                  |      |       | roadways, via |            |
|      |                  |      |       | HAR, VMS and  |            |
|      |                  |      |       | media outlets |            |
+------+------------------+------+-------+---------------+------------+
| High | Drifting snow    | Ala  | Main  | Continuous    | ADOT&PF    |
| w    | will cause road  | ska- | tenan | snow removal. | Maint.     |
| inds | closure at the   | Thom | ce/Tr | Post warning  | Mgmt.      |
|      | pass             | pson | affic | or road       | S          |
|      |                  | Pass | Manag | closure       | ystem/S&IC |
|      |                  |      | ement | signs, as     | Plan.      |
|      |                  |      |       | appropriate,  |            |
|      |                  |      |       | north and     |            |
|      |                  |      |       | south of the  |            |
|      |                  |      |       | Pass.         |            |
+------+------------------+------+-------+---------------+------------+
| High | Forecast         | Or   | Tr    | Advise        | ODOT       |
| w    | crosswind        | egon | affic | truckers via  | Operations |
| inds | greater than 50  | --   | Manag | HAR and VMS   | Plan       |
|      | mph in Ladd      | I-84 | ement | of potential  |            |
|      | Canyon.          |      |       | of winds      |            |
|      |                  | East |       | sufficient to |            |
|      |                  | of   |       | cause         |            |
|      |                  | P    |       | overturning   |            |
|      |                  | endl |       | -- stopping   |            |
|      |                  | eton |       | advised.      |            |
|      |                  |      |       |               |            |
|      |                  |      |       | Upon          |            |
|      |                  |      |       | observation,  |            |
|      |                  |      |       | close road to |            |
|      |                  |      |       | trucks and    |            |
|      |                  |      |       | large loads   |            |
+------+------------------+------+-------+---------------+------------+
| Torn | NS Advisory of   | Okla | Tr    | Provide       | OKDOT      |
| ados | potential for    | homa | affic | advisories to | Traffic    |
|      | tornados within  |      | Manag | travelers via | Operations |
|      | a 60 mile square |      | ement | HAR and VMS   | Plan       |
|      | zone centered on |      |       | to be on      |            |
|      | Enit.            |      | Emer  | alert and     |            |
|      |                  |      | gency | minimize      |            |
|      |                  |      | Manag | travel.       |            |
|      |                  |      | ement |               |            |
|      |                  |      |       | Review        |            |
|      |                  |      |       | response      |            |
|      |                  |      |       | plans in      |            |
|      |                  |      |       | terms of      |            |
|      |                  |      |       | highways and  |            |
|      |                  |      |       | streets       |            |
|      |                  |      |       | affected      |            |
+------+------------------+------+-------+---------------+------------+
| Torn | NWS Warning of   | Ohio | Tr    | Provide       | OKDOT      |
| ados | tornado observed |      | affic | notice to     | Traffic    |
|      | 15mi. SW of      |      | Manag | travelers on  | Operations |
|      | Dayton, and      |      | ement | highways      | Plan       |
|      | within the 60    |      |       | within the    |            |
|      | mi. square zone  |      | Emer  | warning area, |            |
|      | covered by a     |      | gency | via HAR and   |            |
|      | severe           |      | Manag | VMS, to seek  |            |
|      | thunderstorm     |      | ement | shelter.      |            |
|      | warning area     |      |       |               |            |
|      |                  |      |       | Advise        |            |
|      |                  |      |       | everyone,     |            |
|      |                  |      |       | including     |            |
|      |                  |      |       | travelers,    |            |
|      |                  |      |       | via the       |            |
|      |                  |      |       | Emergency     |            |
|      |                  |      |       | Broadcast     |            |
|      |                  |      |       | System, of    |            |
|      |                  |      |       | the threat    |            |
|      |                  |      |       | and to seek   |            |
|      |                  |      |       | shelter       |            |
+------+------------------+------+-------+---------------+------------+
| **   | **Weather        | **Lo | #     | **Solution**  | **Cor      |
| Type | Problem**        | cati | ####  |               | responding |
| of   |                  | on** |       |               | Case       |
| W    |                  |      | #     |               | Study**    |
| eath |                  |      | ####  |               |            |
| er** |                  |      | Profe |               |            |
|      |                  |      | ssion |               |            |
+------+------------------+------+-------+---------------+------------+
| H    | Forecast of      | S    | Tr    | Evacuation.   | SCDOT and  |
| urri | Class 4          | outh | affic |               | FEMA       |
| cane | hurricane with   | Caro | Manag | Undertake     | Hurricane  |
|      | landfall at      | lina | ement | n             | evacuation |
|      | Charleston in 3  |      |       | otifications, | plan.      |
|      | days.            |      | Emer  | and traffic   |            |
|      |                  |      | gency | controls to   |            |
|      |                  |      | Manag | establish all |            |
|      |                  |      | ement | freeway lanes |            |
|      |                  |      |       | northbound    |            |
|      |                  |      | M     | out of        |            |
|      |                  |      | ainte | Charleston    |            |
|      |                  |      | nance | and environs. |            |
|      |                  |      |       |               |            |
|      |                  |      |       | Prepare for   |            |
|      |                  |      |       | clean up.     |            |
+------+------------------+------+-------+---------------+------------+
| H    | Coastal and      | L    | Tr    | Evacuation of | LDOT and   |
| urri | Estuary Flooding | ouis | affic | affected      | FEMA       |
| cane |                  | iana | Manag | areas, and    | hurricane  |
|      |                  |      | ement | advice to     | evacuation |
|      |                  |      |       | travelers via | and        |
|      |                  |      | Emer  | HAR, VMS, and | response   |
|      |                  |      | gency | temporary     | plan.      |
|      |                  |      | Manag | signing on    |            |
|      |                  |      | ement | known flood   |            |
|      |                  |      |       | prone roads.  |            |
|      |                  |      | M     |               |            |
|      |                  |      | ainte | Undertake     |            |
|      |                  |      | nance | notifications |            |
|      |                  |      |       | to initiate   |            |
|      |                  |      |       | evacuations.  |            |
|      |                  |      |       |               |            |
|      |                  |      |       | Prepare for   |            |
|      |                  |      |       | clean up.     |            |
+------+------------------+------+-------+---------------+------------+
| L    | Lightning        | Nort | Emer  | Notify public | NWS COMET  |
| ight | Mapping Array,   | hern | gency | through local | Outreach   |
| ning | multi            | Ala  | Manag | media         | Program    |
|      | ple/dual-Doppler | bama | ement | outlets.      |            |
|      | radar network,   |      |       |               |            |
|      | mobile wind      |      |       |               |            |
|      | profiler, and    |      |       |               |            |
|      | high-resolution  |      |       |               |            |
|      | mesoscale model  |      |       |               |            |
|      | are identifying  |      |       |               |            |
|      | a severe         |      |       |               |            |
|      | lightning        |      |       |               |            |
|      | outbreak.        |      |       |               |            |
+------+------------------+------+-------+---------------+------------+

[^1]: Reductions in free-flow speed (based upon flow rate of 2,400
    vehicles per hour) as reported in Chapter 22 of the 2000 Highway
    Capacity Manual.

[^2]: ^10^ http://www.wsdot.wa.gov/eesc/atb/rwisnews/frames.html

[^3]: ^11^ http://www.srh.noaa.gov/