Low Cost Traffic Engineering Improvements: 

 A Primer 

U.S. Department of Transportation 

Federal Highway Administration 

Office of Transportation Management

April 2003 

1. Report No. 

 FHWA-OP-03-078

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

2. Report Date 

April 2003 

1. Title and Subtitle 

Low Cost Traffic Engineering Improvements: A Primer 

3. Performing Organization Code

 

FHWA

4. Author(s)

Fred E. Latham and Jeffrey W. Trombly 

8. Performing Organization Report No.

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

Science Applications International Corporation 

301 Laboratory Road 

Oak Ridge, TN 37831

11. Contract or Grant No. 

DTFH61-01-C-00180 

13. Type of Report and Period 

Covered

 

Final Report

12. Sponsorship Agency Name and Address 

Department of Transportation 

FHWA Office of Transportation Management 

400 Seventh Street, S.W. - Room 3404 

Washington, DC 20590

14. Sponsoring Agency Code 

FHWA 

15. Supplementary Notes 

Contact Person – Pamela Crenshaw 

16. Abstract 

Transportation agencies throughout the country have implemented various successful and effective low cost strategies to 

improve safety and reduce traffic congestion. 

17. Key Words 

 

Traffic Engineering Improvements 

18. Distribution Statement 

No restrictions. This document is available to the public from 

National Technical Information Service 

Springfield, Virginia 22161

19. Security Classif. (of this 

report) 

Unclassified

20. Security Classif. (of this 

page) 

Unclassified

21. No. of 

Pages 

 15 

22. Price

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

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TABLE OF CONTENTS 

Acronyms .............................................................................................................................................vi 

Introduction and Purpose................................................................................................................... 1 

What are Low Cost Traffic Engineering Improvements?.............................................................. 2 

Why are Low Cost Traffic Engineering Improvements Important?............................................ 5 

What Agencies are Using Low Cost Improvements?..................................................................... 5 

Innovative Low Cost Strategies .......................................................................................................10 

Low Cost Improvements for Rural Roads.....................................................................................12 

Conclusion ..........................................................................................................................................14 

References ...........................................................................................................................................15 

Figures 

Figure 1, Pennsylvania DOT Intersection Warning Treatment..................................................12 

Tables 

Table 1, Additional Examples of Low Cost Traffic Engineering Improvements...................... 4 

Table 2, Springfield, Missouri Intersection Problem Treatments................................................. 6 

Table 3, Selected Intersections Treated as Part of AAA Michigan Program.............................. 7 

Table 4, Examples of Low Cost Implementations by 

 Maryland State Highway Administration .......................................................................... 8 

Table 5, Sample Problems Treated by Pennsylvania DOT ........................................................... 9 

Table 6, Pennsylvania DOT Innovative Low Cost Improvements............................................10 

Appendix 

Guidelines for Installation of Pennsylvania “Dot” Tailgating Treatment.................................17 
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Acronyms 

DOT Department of Transportation 

MDSHA Maryland State Highway Administration 

NYSDOT New York State Department of Transportation 

NYSTA New York State Thruway Authority 
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Introduction and Purpose

This report presents the results of an investigation into low cost traffic engineering improvements, including 

types of actions, costs, and benefits. 

In an effort to reduce crashes and ease traffic congestion on our nation’s 

highways, traffic engineers and planners have traditionally pursued a wide range 

of actions. In some cases, the most cost-effective solution requires a significant 

investment in public funds. In other cases, the most cost-effective solution can 

be achieved through implementation of lower cost solutions. The purpose of 

this report is to share approaches that have been implemented to provide low 

cost solutions for improving safety and traffic flow. The report is designed to 

serve as a primer, or basic introduction, to the subject of low cost traffic 

engineering improvements. The goal is to provide practicing traffic engineers 

and planners with information describing the types of low cost actions that have 

been implemented, along with their cost and benefits. 

“Low cost” is a relative term. Agencies implementing large projects with large 

budgets may perceive a “low cost” project differently than an agency with a 

limited budget. For purposes of this discussion, “low cost” is defined as a 

project or strategy that generally requires an investment in the range of $10,000 

to $50,000. Many of the strategies discussed range from several hundred dollars 

to several thousand dollars in magnitude. The research conducted for this study, 

however, indicates that “low cost” does not mean “low benefit.” 

The research results presented in this report are based on a review of the 

literature as well as interviews with transportation agency staff throughout the 

nation. The results identify a series of successful and effective low cost strategies 

that agencies have implemented to improve safety and reduce traffic congestion. 

Hopefully, many of the practices presented are transferable to other communities 

dealing with similar problems. 

This report is divided into five parts. Following this introductory section, the 

second part describes several low cost traffic engineering improvements that 

have been implemented in a variety of locations. The third part of this report 

discusses why low cost traffic engineering improvements are important. Among 

the most significant reasons cited for pursuing low cost improvements is that 

limited funding is available to local jurisdictions for managing growing safety and 

capacity problems. The fourth part of this report examines the benefits that 

have been derived from the implementation of low cost improvements based on 

several examples that have been implemented in different parts of the nation. 

The fifth part of this report describes several experimental or innovative low cost 

approaches to increasing safety and mitigating congestion. 
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What Are Low Cost Traffic Engineering Improvements?

Research has confirmed that low cost, shorter-term strategies that utilize shoulders, narrow lanes, regulatory 

devices, and technology to manage travel and control traffic can increase capacity and improve operations and 

safety at a particular bottleneck along a congested metropolitan corridor. 

Low cost traffic engineering improvement techniques are typically spot 

applications or are limited to shorter sections of roadway that do not cover an 

entire length of an arterial corridor. Some of these strategies include pavement 

markings, static and dynamic signing, roadway lighting, raised medians, curb cuts, 

roadway geometric changes, or lane controls. These strategies provide the 

guidance, warning, and control needed for drivers to ensure safe and informed 

operation through traffic bottlenecks or congested areas. 

An understanding of the types of low cost actions that have been implemented is 

best gained through the examination of several successful programs, including 

the Automobile Club of Michigan (AAA Michigan); the Traffic Engineering 

Department of the City of Winston Salem, North Carolina; and the Traffic 

Engineering Department of the City of Knoxville, Tennessee. 

AAA Michigan initiated a program to identify and treat locations in the cities of 

Detroit and Grand Rapids with frequent crashes. Over the past six years, AAA 

Michigan examined 253 intersections in Detroit and Grand Rapids and 

implemented low cost safety improvements at 112 sites. Actions implemented at 

the intersections included the following: 

 implementation of all-red intervals; 

 replacement of 8-inch signal heads with 12-inch signal heads; 

 relocation of signal heads to improve visibility by realigning two signal 

heads facing each other, realigning the signal heads over each lane of 

travel, or mounting the signal heads using box span installations; 

 installation of secondary post-mounted signal heads to improve visibility 

at some locations; 

 installation of back plates on traffic signals to improve visibility at some 

locations; 

 installation of left turn lanes through re-striping of approach lanes and 

exclusive left turn phases, where needed; and 

 removal of on-street parking. 

Post-implementation crash studies conducted for improvements in Detroit 

showed a greater than 50% reduction in total crashes and a greater than 60% 

reduction in total injuries at the treated intersections. A benefit-cost study 

conducted as part of the project found a 15:1 return for the Detroit intersection 

improvements and a 16:1 return for the Grand Rapid intersections. 
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In 1986, the Traffic Engineering Division of the City of Winston Salem, North 

Carolina began an annual program to locate and treat crash locations and 

evaluate the results of such treatments. Over time, the program has completed 

before-and-after studies at 364 locations, adding 40 to 50 new locations each 

year. As a result, the program has reduced targeted crashes by 49% and total 

crashes by 13%. 

Low cost treatments implemented at high crash locations included the following: 

 creating a left turn lane within the confines of an existing roadway, 

 adding left turn phases to existing signals, 

 replacing “Yield” signs with “Stop” signs at intersections, 

 replacing two-way stops with multi-way stops, 

 installing traffic signals, 

 using bigger and/or better signs, 

 installing short segments of center line and stop bars at “Stop” locations, 

 installing double-indicating “Stop” signs (adding a left-side sign), 

 painting the message “Stop Ahead” and “Stop” on pavement, 

 removing signals from late night/early morning programmed flashing 

operation, 

 adding back plates to existing signal installations, 

 adding a signal head to an existing display, 

 replacing 8-inch signal heads with 12-inch signal heads, 

 adding “Signal Ahead” signs, 

 installing red “T” displays (two red signal heads mounted horizontally 

over an amber and green), 

 installing an all-red interval, and 

 replacing protected/permissive left turn phases with full protected left 

turn phases. 

The City of Knoxville, Tennessee, Traffic Engineering Department has 

successfully implemented a number of low cost traffic engineering improvements 

over the years. Examples include the following: 

 installing sight distance mirrors where more expensive earthwork to 

remove the sight distance obstacle is not feasible, 

 installing strobe lights in signals to make the public more aware of signals 

that are present in areas where background lighting is present, 

 providing longer all-red intervals in the signal timing where such things as 

bridge decks interfere with signals, 

 placing signal heads to provide a better view of red signals in limited 

sight-distance-to-signal faces, 

 providing narrower lane widths to provide additional lanes, 

 providing narrower lane widths to allow for a pedestrian island, and 

 providing detector actuated flashers for sight distance problems that 

would require very expensive earthwork to correct sight distance 

problem. 
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Two state agencies in New York, New York State Department of Transportation 

(NYSDOT) and the New York State Thruway Authority (NYSTA), installed 

continuous shoulder milled rumble strips during the 1990s. NYSDOT installed 

approximately 8,000 shoulder-kilometers of continuous shoulder rumble strips 

along its existing rural interstate highways and parkways throughout the state 

between 1993 and 1998. During the same period, the NYSTA installed 3,131 

shoulder kilometers of rumble strips on 81% of the New York Thruway (3,864 

shoulder-kilometers) between 1992 and 1996. 

Both agencies evaluated the effectiveness of continuous shoulder rumble strips 

by collecting data before and after the installation. They both concluded that the 

installation of the continuous shoulder rumble strips reduced the number of 

crashes by at least 65% to 70%. Particularly, NYSTA noted that the number of 

run-off-road crashes was reduced by 88% (557 cases in 1991 versus 74 cases in 

1997), and fatalities declined by 95% (17 cases in 1991 versus 1 case in 1997). 

With improved manufacturing efficiencies and increased numbers of 

installations, the cost of purchasing and installing milled rumble strips has 

dramatically decreased over the years. For example, NYSTA reports that the 

linear meter cost of a milled rumble strip was $3.63 in 1993 compared to $0.38 in 

1996. These costs do not include maintenance and protection of traffic. 

Table 1 contains several more examples of low cost traffic engineering 

improvements that have been implemented across the country. These actions 

include restriping pavement to provide additional travel lanes, landscaping to 

remove restrictions to sight distance, and installing improved signage to reduce 

crashes. 

Table 1 

Additional Examples of Low Cost Traffic Engineering Improvements 

Location Description 

Barnstead, New Hampshire Installed warning signs/beacons at intersection of 

Route 288 and N. Barnstead Rd. 

Hampton, New Hampshire Restriped and narrowed lanes on New Hampshire 

Route 111 to 11 feet to provide wider bike lanes 

New Hampshire, various locations Installed and placed driver speed feedback signs at 

various locations 

Bow, New Hampshire Restriping pavement to provide an auxiliary lane to 

convert an on- and off-ramp into a weave at 

interchange of I-89 and I-93 

Orlando, Florida Removed and landscaped approaches to improve sight 

distance at first median cut west of John Young 

Parkway on Town Center Boulevard due to high 

collision rate related to inadequate sight distance 

Glenlig, Maryland Created left turn lanes with striping and a short bulbout section on Route 32 

Stuart, Florida Reduced number of median openings on U.S. 

Route 1 
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Why Are Low Cost Traffic Engineering Improvements Important?

Low cost traffic engineering improvements offer local traffic engineers means for improving safety in the face of 

increasing traffic volumes and decreasing budgets for traffic improvements. 

Demand for highway travel by Americans continues to grow as population 

increases, particularly in metropolitan areas. Construction of new highway 

capacity to accommodate this growth in travel has not kept pace. Between 1980 

and 1999, route miles of highways increased 1.5% while vehicle miles of travel 

increased 76%. The Texas Transportation Institute estimates that in 2000, the 75 

largest metropolitan areas experienced 3.6 billion vehicle hours of delay, resulting 

in 21.6 billion liters (5.7 billion gallons) of wasted fuel and $67.5 billion in lost 

productivity. Traffic volumes are projected to continue to grow. Congestion is 

largely thought of as a big city problem, but delays are becoming increasingly 

common in small cities and some rural areas as well. 

There is a need to provide tools and information on modest traffic 

improvements (roadway geometry, signage, striping, etc.) that can be 

implemented by state and local traffic engineers to reduce traffic congestion and 

improve traffic flow. Budget constraints in the face of continually increasing 

safety and congestion problems have meant that local traffic engineers need to 

apply low cost solutions wherever feasible. As the examples presented in this 

report show, these solutions cover a wide range of actions. 

What Agencies Are Using Low Cost Improvements? 

Automobile clubs, municipal agencies, and state transportation departments have all applied low cost traffic 

engineering solutions. 

Low cost improvements are another set of tools available to traffic engineers to 

mitigate increasing traffic congestion and to reduce crashes. They are best 

viewed as one of a number of strategies that can be employed by the practicing 

traffic engineer to effectively and efficiently manage traffic. The research 

conducted for this study found a number of public and private agencies that have 

adopted low cost traffic engineering solutions as a continuing part of their 

programs. 

City of Portland, Oregon 

Traffic circles have been an integral part 

of the City of Portland's Traffic 

Management Program for approximately 

five years. Portland has utilized traffic 

circles to reduce vehicle speeds and 

eliminate very fast traffic on local 

residential streets. Traffic circles are 

frequently chosen over other devices 

because they do not divert truly local 

traffic and do not restrict access to 

Traffic circles were 

effective in reducing 

speeds on 

residential streets in 

Portland. 
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6 

adjacent streets or land uses. 

Experience in Portland and other cities in 

the U.S. and Europe indicates that traffic 

circles are effective in reducing vehicle 

speeds and can reduce the number and 

severity of intersection accidents. 

An evaluation by the City of Portland to 

determine the impact of traffic circles 

and their potential effect on traffic 

speeds and intersection safety 

substantiates the finding that traffic 

circles are successful at reducing the 

number of vehicles traveling at high speeds (30-35 mph) on residential streets. 

On many of Portland’s residential streets, 15% or more of the vehicles routinely 

exceeded 35 mph. After traffic circles were installed, vehicles rarely exceed 35 

mph. The larger circles (12-foot radius) appear to reduce vehicle speeds more 

than smaller traffic circle islands. Moreover, the analysis found that traffic circles

have dramatically reduced, if not almost eliminated, reported accidents, especially 

multi-vehicle collisions. The cost to construct each circle ranges from $3,000 to 

$9,000. 

Springfield, Missouri 

The Public Works Department of the City of Springfield, Missouri routinely 

installed and evaluated low cost traffic engineering improvements to correct 

safety problems at intersections. As presented in Table 2, these treatments range 

in cost from $150 to $5,000. 

The Department of Public Works continues to install and monitor the 

effectiveness of various intersection improvement strategies and report this 

information to city management. 

Table 2 

Springfield, Missouri Intersection Problem Treatments

Problem Description Cost 

Poor signal head visibility 

attributed to side mounted 

signals 

Install mast arm to mount signal heads 

overhead to improve visibility 

$5,000

Illegal turning-left 

movements 

Install lane use signs $150

Poor alignment of 

overhead flashing signal at 

four-way-stop controlled 

intersection 

Realign signal and relocate “Stop 

Ahead” sign to improve visibility 

$300

Crashes by drivers turning 

left at signalized 

intersection 

Install protected phase $1,500

Portland has used traffic circles like the 

one shown above for approximately five 

years, dramatically reducing multivehicle crashes.
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AAA Michigan 

AAA Michigan selected locations for improvements based on high levels of 

crashes. Midblock crashes along the studied corridors were insignificant when 

compared with the crashes at signalized intersections; therefore, midblock crash 

treatments were not targeted for implementation, and the focus of the effort was 

placed on improving signalized intersections. The improvements implemented 

varied by location; however, in general, they were low cost improvements on the 

order of approximately $30,000 per intersection (Table 3). 

Table 3 

Selected Intersections Treated as Part of AAA Michigan Program

Intersection City Description Cost 

Crash 

Reduction 

Seven Mile Road 

and John R. 

Road 

Detroit Approach lanes re-striped to include 

left turn lanes at the north, south, 

and eastbound approaches. In 

addition, an exclusive left-turn phase 

for the east-west traffic was installed 

using a three-phase design. Parking 

was removed for 200 feet of clear 

sight distance. Signal heads were 

upgraded from 8-inch to 12-inch 

signal heads, and all-red intervals of 

sufficient length were added. 

$35,200 50% 

Seven Mile Road 

and Ryan Road 

Detroit Exclusive left turn lanes were 

installed along with exclusive left 

turn phases. No roadway widening 

was required because existing 

pavement width was available. The 

traffic signals were upgraded from 8-

inch to 12-inch diameter signal 

heads, and all-red intervals of 

sufficient length were installed. Onstreet parking was removed, 

providing approximately 200 feet of 

clear sight distance. 

$36,100 53% 

Hubble Road 

and Puritan Road 

Detroit Left turn lanes were installed at all 

approaches. The traffic signals were 

upgraded from 8-inch to 12-inch 

diameter signal heads, and all-red 

intervals of sufficient length were 

installed. 

$30,300 64% 

Treatments used in 

Springfield 

included installing 

a protected phase 

(left) and overhead 

signals (right). 
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Maryland State Highway Administration 

The Maryland State Highway Administration (MDSHA) works to improve 

mobility through non-traditional signal timing improvements (Table 4). With 

considerable peak period main line traffic flowing to and from Washington D.C., 

engineers are challenged to maintain traffic flow while providing adequate service 

to local and side street traffic. 

Table 4 

Examples of Innovative Low Cost Implementations by 

Maryland State Highway Administration 

Problem Treatment Approximate 

Cost 

Mainline congestion resulting 

from inadequate storage capacity

Two exclusive left turns 

allowed per cycle 

$5,000 per 

intersection 

Lengthy delays for minor 

movements 

Half-cycle variation $5,000 per 

intersection 

Lengthy mainline queues and 

congestion 

Directional lead-lag $5,000 per 

intersection 

Signal Timing Improvements 

Two turn phases per cycle – In situations where main line peak period flow 

requires an extended green period, left turn lanes that are not permissive can extend 

beyond the storage area, causing disruption to main line traffic flow. In these 

situations, MDSHA has begun allowing for two exclusive left turn lane periods per 

main line cycle. The lead- and lag-exclusive left turn is activated in the direction of 

peak period traffic flow. This has proven to be an effective, low cost method to 

improve mobility. The process requires the controller to be reprogrammed. The 

total cost is below $5,000, with half for reprogramming the controller and half for 

engineering assessment of the intersection and potential treatments. 

Half-cycle variation – A variation of the “half cycle” is used to decrease delays for 

minor movements while maintaining traffic flow on the main line. A 3-minute cycle 

will consist of one long mainline movement, then a side street movement, another 

short mainline movement, and another side street movement. This variation is 

useful when developing progression on two consecutive intersections with different 

cycle lengths. Synchronization software is utilized to assess signal cycles prior to 

implementation. The innovative signal cycle improves main line traffic flow at a cost 

of less than $5,000. 

Directional lead-lag – At intersections where only exclusive left turns are 

allowed, MDSHA has begun to use a signal cycle called “directional lead-lag”. By 

utilizing signal synchronization software, the process allows one directionexclusive left turn and mainline traffic flow during the lead phase, allowing the 

other direction-exclusive left turn and mainline movement during the lag phase 

of the green band. Field assessments have shown this to double the duration of 

green bands, reduce queues, and reduce unnecessary stop time. The innovative 

signal cycle improves main line traffic flow at a cost of less than $5,000. 
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Pennsylvania Department of Transportation 

The Pennsylvania Department of Transportation (DOT) developed a program of 

low cost safety improvements as an element of its Safety Management Plan 

(Table 5). Improvements were targeted at high crash locations. Funds were made 

available to implement a variety of low cost actions, including the following: 

 pedestrian channelization devices and addition of a 3-second advance for 

pedestrians at signalized intersections, 

 centerline rumble strips where concentrations of head-on crashes 

occurred on two-lane highways, and 

 removal or delineation of trees or utility poles where the concentration of 

crashes involving trees occurs in a set segment of highway. 

Table 5 

Sample Problems Treated by Pennsylvania DOT 

Centerline milled rumble strips are designed to reduce the incidence of drivers 

crossing into the opposing travel lane by using the sound and sensation of 

encroachment across the centerline to alert them. This treatment costs 

approximately $5,000 per mile and is effective in reducing the frequency of 

head-on crashes. 

A variety of low cost pedestrian safety treatments have been applied by the 

Pennsylvania DOT, including time extensions for pedestrians at signalized 

intersections to give pedestrians a three-second head start when crossing, 

installation of “Stop for Pedestrians in Crosswalk” sandwich boards, and 

exclusive pedestrian phases at intersections with a high level of pedestrian and 

vehicle crashes. 

Pennsylvania DOT has also installed delineation treatments on roadside 

obstacles, such as utility poles. While these are very inexpensive treatments, they 

have proven to be effective in reducing fixed-object crashes. 

Problem Treatment Approximate Cost 

Head-on 

crashes 

Centerline rumble strips $5,000 per mile 

Fixed objects 

on roadside 

Tree delineation utility pole delineation 

Shoulder rumble strips 

$90 per pole 

$3/linear foot 

Pedestrian 

safety 

3-second advance for pedestrians at 

signalized intersections 

$5,000 per intersection 

Pennsylvania DOT used centerline milled rumble 

strips (left) and pedestrian treatments (right) as 

elements of its Safety Management Plan. 
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Innovative Low Cost Strategies 

Case study data shows the effectiveness of the low-cost approach in creating safe driving conditions for 

motorists. 

The Pennsylvania DOT has designed and implemented several innovative 

strategies to treat safety problems. Many of these approaches reflect a low cost 

approach to traffic engineering. As presented in Table 6, these strategies are 

generally designed to improve safety through improved signing and pavement 

marking programs. 

Table 6 

Pennsylvania DOT Innovative Low Cost Improvements 

Treatment Description Cost Effectiveness 

Advance 

curve warning 

Developed to help 

motorists reduce speed 

when approaching curve. 

The pavement marking 

consists of two transverse 

bars, a “SLOW” legend, 

and an arrow indicating the 

direction of the upcoming 

curve. 

Approximately 

$1,350 per site 

Based on the evaluation of 

the original pilot program, 

there is expected to be a 

reduction of the 90th

percentile speed. This 

translates into an estimated 

25% reduction in curverelated deaths at each of 

the locations where 

installation is planned. 

“Dot” 

tailgating 

treatment 

Idea is to reduce tailgating 

by installing “dot” shaped 

pavement markings at 

fixed intervals such that 

keeping two markings 

apart will provide a safe 

following distance. 

Approximately 

$1,800 per site 

Police in South Centre 

Township observed a 

significant drop in 

tailgating and speeding in 

the area of the dots. 

Intersection 

warning 

treatment 

Concept is to provide 

advance warning to drivers 

proceeding through 

intersections under 

“Stop”- sign control. A 

series of signs and 

pavement markings assist 

drivers in judging gaps 

between on-coming 

vehicles. 

Approximately 

$5,000 per 

intersection 

Experimental program 

under evaluation. 

Pennsylvania DOT’s Advanced Curve Warning Treatment 

The advanced curve warning treatment is a pavement 

marking placed on the roadway indicating that the 

driver should reduce speed for an upcoming curve. 

This treatment is being promoted in sections of roads 

or corridors with higher than average numbers of 

crashes having roadway curvature as a contributing 

factor. The pavement marking consists of two 

transverse bars, a “SLOW” legend and an arrow 

indicating the direction of the upcoming curve. The advanced curve warning treatment

warns drivers to reduce speeds.
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11 

The overall objective is to reduce the upper percentile speed, thus reducing the 

number of vehicles leaving the roadway and being involved in a crash. The total 

estimated cost per site, including pavement markings, installation labor, and 

equipment was approximately $1,350. Based on the evaluation of the original 

pilot program, there is expected to be a reduction of the 90th percentile speed. 

This translates into an estimated 25% reduction in curve-related deaths at each 

location where installation is planned. The larger pilot involves the treatment of 

nearly 200 sites with the advanced curve warning treatment. 

Pennsylvania DOT’s “Dot” Tailgating Treatment 

The “dot” tailgating treatment marking is an effective highway safety 

countermeasure for assisting motorists in establishing safe following distances. 

This treatment is being promoted in sections of roads or corridors with higher 

than average numbers of crashes linked to aggressive driving or tailgating and 

where traffic congestion is not anticipated. Markings are spaced such that a 

minimum of two markings separates vehicles, which allows for a safe distance 

between them. Initially the Department tried painted chevrons on the pavement, 

with the spacing between chevrons based on the 2-second rule; however, the 

public had some difficulty in understanding what the chevrons meant. To 

address tailgating crash 

problems and motorists’ 

confusion with chevrons, the 

Department decided to identify 

the area with signing and dot 

pavement markings, educate the 

motoring public with press 

releases and media events, and 

have targeted additional 

enforcement at particular 

problem areas in the corridor. 

The total cost per installation is approximately $1,892 including signs, labor, and 

equipment. A test site was deployed in South Center Township since rear-end 

crashes represented 43% of the crashes on the US 11 corridor. South Centre 

Township police reported that they have observed a significant drop in tailgating 

and speeding in the area of the dots, and in the area north of the dots there has 

been a 60% drop in crashes based on a comparison of the following time 

periods: 

 11/1/99 to 3/1/00 = 34 crashes 

 11/1/00 to 3/1/01 = 12 crashes 

The appendix to this primer contains the Guidelines for Installation of 

Pennsylvania “Dot” Tailgating Treatment and Design Specifications. 

Dot treatment 

signage 

indicates safe 

following 

distances. 
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Figure 1. Pennsylvania DOT

Intersection Warning 

Treatment. Roadway markings 

help guide drivers where 

roadways intersect at grade. 

Pennsylvania DOT Intersection Warning 

Treatment 

This treatment is used on a pilot basis 

when data show a high occurrence of 

crashes where vehicles on secondary 

roadways intersecting at grade misjudge 

the gap between approaching vehicles. 

Markings are placed to indicate safe gap 

length for a vehicle to accelerate from a 

stop into the intersection. Safe distance is 

defined based on posted speed for the 

primary roadway. The entire treatment 

consists of the following components: 1) 

placement of legend “SLOW, xxMPH” 

and 2) “+” symbols on the primary 

roadway, and 3) placement of 

appropriate signs on the 

secondary roadway. 

Low Cost Improvements for Rural Roads 

On rural roads, low cost treatments have been used to address run-off-the-road crashes and to improve 

visibility. 

Numerous low cost traffic-engineering improvements have been made to rural 

two-lane roads. Many of these treatments are designed to reduce the number of 

run-off-the–road crashes that account for a significant share of crashes in rural 

areas. Treatments installed include the following: 

 bigger and brighter curve and chevron signs, 

 inside- and outside-curve paved shoulder with rumble strips, 

 rumble warning panels in advance of curves, 

 shoulder edge drop-offs, 

 installation of paved shoulders, 

 brighter and more durable pavement markings, and 

 flattened slopes. 

It becomes more important to consider improvements to signs, signals, and 

markings to improve visibility as the rural population ages. Example low cost 

treatments that have been implemented to improve the visibility of traffic control 

devices include the following: 

 installing larger stop signs, 

 placing flags on stop ahead and stop signs, 

 placing a flashing beacon on stop signs, 

 installing advance stop sign rumble strips, and 

 installing larger 8-inch street name signs. 
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Arlington County, Virginia Department of Public Works 

The “intelligent” pedestrian crosswalk is a state-of-the-art system that provides 

additional pedestrian safety at high volume mid-block locations. The system uses 

sensor technology to trigger a set of lights, which are located along the marked 

crosswalk. The signals warn motorists that a pedestrian is in the crosswalk. This 

passive system uses an infrared eye with a one-directional setup to avoid 

extended activation as pedestrians clear the crosswalk. Timing is set using 

standard federal guidelines for crosswalk clearance times. The system in 

Arlington cost approximately $9,800 dollars, with an additional $10,000 in labor 

for installation. It has a 10-year life expectancy. 

Maryland State Highway Administration 

Route 4 North toward Washington, D.C. carries a significant volume of traffic to 

I-495, the National Capitol Beltway, and to downtown destinations during the 

morning peak period. The three-lane route is limited to two lanes in both 

directions 1.5 miles south of I-495. To eliminate the bottleneck created by the 

lane reduction, MDSHA needed an innovative, low cost method of maintaining 

adequate capacity. Using signage and pavement markings, peak period traffic is 

directed to use shoulders, thus relieving congestion. In the southbound direction, 

MDSHA has extended an on-ramp, allowing traffic to use the shoulder. 

Confirming signs are used to indicate the special use provision. 

Chevron signs Night performance pavement markings Flags on stop sign

Rumble warning panel Before slope flattening After slope flattening

Shoulder use on Route 4 

is permitted during peak 

periods (left). Signage 

indicates the end of the 

special use provision 

(right). 
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Conclusion 

Low cost engineering traffic improvements have mitigated congestion and increased safety in communities 

across the country. 

Among the solutions available to engineers and planners to ease traffic 

congestion and increase safety are a number of “low cost” solutions. These are 

projects or strategies that require investments ranging from several hundred 

dollars to roughly $50,000. 

Treatments to achieve a more effective traffic flow include various executions of 

these techniques: 

 innovative signal timing, 

 narrower lane widths to allow for more lanes, 

 shoulder usage during peak periods, 

 exclusive left turn lanes and left turn phases, and 

 on-street parking removals or reductions. 

A number of transportation agencies have quantifiably reduced injuries and 

crashes by taking these actions: 

 constructing pedestrian islands, 

 installing pedestrian sensors in crosswalks, 

 installing more visible traffic signals and signs, 

 installing rumble strips, 

 using traffic circles to reduce traffic speed, 

 removing or delineating trees and utility poles, 

 using advanced warning pavement markings, and 

 using pavement markings in conjunction with a public awareness 

program to reduce tailgating. 

While these examples, along with others presented in this primer, illustrate 

relatively inexpensive approaches, they have proven to be effective in mitigating 

congestion and increasing safety in communities across the country. 
L o w C o s t E n g I n e e r I n g T r a f f I c I m p r o v e m e n t s

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References 

Crawford, B., “PennDOT’s Highway Safety Countermeasure Evaluations.” 

Unpublished Powerpoint presentation. 

Datta, T. and Kerrie Schattler. Evaluation Studies for the AAA Road Improvement 

Demonstration Program in Michigan Interim Report. Wayne State University 

Department of Civil and Environmental Engineering, October 2002. 

G. D. Hamilton Associates Ltd, AAA Road Improvement Demonstration Program 

Evaluation Phase 2: Detroit and Grand Rapids, Michigan. Hamilton and Associates, 

October 2002. 

Modi, G. “Low Cost Safety Improvements.” Presentation at Institute of 

Transportation Engineers 2002 Annual Meeting, August 2002. 

Polanis, Stanley F. “Low Cost Safety Improvements: What are They, How Do 

They Fit Into Safety Efforts & Do They Work?” TM+E Magazine, Volume 6, 

Number 5, (October/November 2001). 

Welch, T. “Cost Effective Approaches to Improving Safety on Rural Roads.” 

Unpublished Powerpoint presentation, October 2002. 
L o w C o s t E n g I n e e r I n g T r a f f I c I m p r o v e m e n t s

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L o w C o s t E n g I n e e r I n g T r a f f I c I m p r o v e m e n t s

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Appendix 

Guidelines for Installation of Pennsylvania “Dot” Tailgating Treatment 

1. The “dot” markings are shown to be effective for assisting the motorist in establishing 

safe following distance. Use this treatment in areas where there is a high concentration of 

aggressive driving or tailgating-related crashes. Markings are spaced such that safe 

distance is kept between vehicles when a minimum of two markings separates them. Safe 

distance is defined based on a two-second following rule. Areas with significant grade 

differences should generally be avoided. 

2. Marking - The marking consists of a series of ellipses (dots) marked in all lanes at equal 

spacing according to the posted roadway speed (see Table 1, Spacing ‘S’). Marking is to 

be centered in the travel lane. The ratio of width to height for the elliptical mark is 1:3 

based on standard oblong pavement markings referenced in the MUTCD. Markings 

should be applied according to Figure 1. 

3. Spacing - The pavement markings should be placed such that the spacing is according 

to Table 1. Spacing is based on posted speed for any given roadway. 

4. Pattern Spacing - The distance between successive series of dots is also based on 

posted speed and can be found in the Table 1. This distance should be adjusted as 

appropriate to meet field conditions. 

5. Signing - There should be placed a minimum of three signs as follows: 

• “Don’t Tailgate” should be placed 1,000 feet before the first pattern. 

• “Keep Min 2 Dots Apart” sign should be placed at the second marking in each set of 

dots. 

• “Maintain Safe Following Distance,” sign should be placed 1,000 feet after the last 

pattern. 

For signing layout, see Figure 3. Place signs in accordance with Sign Foreman’s 

Manual, Pub 108. 

6. Refer to the attached Specification for Epoxy Pavement Marking for selection of 

material and construction. 

7. Dot pavement markings can be installed via projects initiated exclusively for this 

purpose. 

Deviation from the above specifications and guidelines may be considered by 

Districts; however, they require approval by the Bureau of Highway Safety & 

Traffic Engineering prior to implementation. 
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L o w C o s t E n g I n e e r I n g T r a f f I c I m p r o v e m e n t s

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Pennsylvania "DOT" Tailgating Treatment

Comprehension Time : 5 sec

P/R Time : 2.5 sec

Adjustment Time : 20 sec

Following Time : 2 sec

Effective Time : 60 sec

Vehicle Correction : 15 ft

S LX

Posted 

Speed 

(mph)

Posted 

Speed 

(fps)

Distance 

Travelled 

(ft)

Marking 

Spacing 

(ft)

Minimum # 

Markings in 

Pattern

Min Pattern 

Length 

(ft)

Pattern 

Spacing 

(ft)

25 37 73 60 18 1020 2200

30 44 88 75 18 1275 2640

35 51 103 90 17 1440 3080

40 59 117 105 17 1680 3520

45 66 132 115 17 1840 3960

50 73 147 130 17 2080 4400

55 81 161 145 17 2320 4840

60 88 176 160 17 2560 5280

65 95 191 175 16 2625 5720

Table 1 - Spacing and Length

Definitions

P/R Time

(sec)

Adjustment Time

(sec)

This Distance reflects the spacing between two pavement markings within the pattern such that vehicle will 

traverse two markings in the Following Time . Value is equal to Distance Traveled (ft) rounded to the next 5 

foot length less the Vehicle Correction 

Marking Spacing, S

(ft)

Following Time

(sec)

Effective Time

(sec)

Posted Speed

(fps)

Distance Traveled

(ft)

Comprehension Time

(sec)

Amount of Time required for driver to comprehend the meaning of the markings.

Indicates Time required for an average driver on target roadway to percieve that an action is required and to 

begin that action. Typical Value is 2.5 seconds.

Amount of Time provided for the following driver to gauge and adjust the Distance between their vehicle and 

the lead vehicle.

Distance a vehicle will travel between Marking Patterns. Relates to Effective Time such that the effect of the 

previous set of markings will just begin to fade as driver encounters the next set. Value is Posted Speed 

(fps) times Effective Time (sec) .

The enforcable following time for target roadway. Vehicles should travel a Distance apart from each other 

such that this Time has passed for a following vehicle to reach the location of the lead vehicle at Time t0.

Length of Time for which the pattern maintains an effect on the driver. Relates to how long the driver can 

maintain the Distance corresponding to the Following Time after leaving the pattern.

Relates to the Posted Speed Limit on the target roadway.

At the given Posted Speed , this indicates the Distance the vehicle will travel in the Following Time . Value is 

Posted Speed (fps) times Following Time (sec) .

Distance vehicle must be away from the nearest DOT to allow the DOT to be visible from the drivers eye 

position. Value assumed to be 15 ft measured from bumper to edge of DOT marking.

Distance from the center of the first marking in the pattern to the center of the last marking in the pattern. 

Value is the Number of Markings , less one, times Marking Spacing .

The number of markings at the Marking Spacing that can be placed in the length of roadway required to 

travel at the Posted Speed for the total required Comprehension, P/R, and Adjustment Times. Value is that 

length (ft) divided by Marking Spacing (ft) rou

Vehicle Correction

(ft)

# Markings in Pattern

Pattern Length, L

(ft)

Pattern Spacing, X

(ft)

S

L

X
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Pennsylvania “DOT” Tailgating Treatment 

Alternative A (ft) B (ft) Area (sq ft) 

Two Lane Highway 7.5 2.5 14.71 

Interstate 12 4 37.68 

* Refer to Guidelines for more information 

Figure 1 – Typical Marking 

Typical Marking 

B A 

Width:Length = 1:3 ratio* 
L o w C o s t E n g I n e e r I n g T r a f f I c I m p r o v e m e n t s

21 

L 

S

X

MAINTAIN SAFE 

FOLLOWING 

DISTANCE

DON’T 

TAILGATE 

At second dot 

marking 

1,000 feet before 

first pattern 

1,000 feet after last 

pattern 

Figure 3 Sign and 

Pattern Layout

KEEP MIN 

 2 DOTS APART