Paper No. 09-0488 

THE BENEFITS OF PAVEMENT MARKINGS: 

A RENEWED PERSPECTIVE BASED ON 

RECENT AND ONGOING RESEARCH 

Paul J. Carlson, Ph.D., P.E.* 

Research Engineer 

Texas Transportation Institute 

The Texas A&M University System 

3135 TAMU 

College Station, TX 77843-3135 

979-845-6004 (office) 

979-845-6006 (fax) 

paul-carlson@tamu.edu 

Eun Sug Park, Ph.D. 

Associate Research Scientist 

Texas Transportation Institute 

The Texas A&M University System 

3135 TAMU 

College Station, TX 77843-3135 

(979) 845-9942 

e-park@tamu.edu 

Carl K. Andersen 

Roadway Team Leader 

Office of Safety Research and Development 

Turner-Fairbank Highway Research Center 

Federal Highway Administration 

6300 Georgetown Pike 

McLean, VA 22101 

(202) 493-3366 

carl.andersen@fhwa.dot.gov 

* Corresponding Author 

August 1 2008 

Word Count: 7,287 

For TRB 88th Annual Meeting 

(January 11-15, 2009)
Carlson, Park, and Andersen Page 2 of 21 

ABSTRACT 

One of the most important aspects of a safe and efficient roadway is the uniform application of 

pavement markings to delineate the roadway path and specific traffic lanes. Pavement markings 

can communicate information to road users like no other traffic control device. They provide 

continuous information to road users related to the roadway alignment, vehicle positioning, and 

other important driving-related tasks. 

It is estimated that in the United States alone, approximately $2 billion is spent annually on 

pavement markings. Despite these annual expenditures, there is a general void in terms of a 

consolidated effort that attempts to quantify proven benefits of pavement markings. Over the 

years, many research projects have focused on specific elements of pavement markings. This 

paper was developed to bring together many of the recent and ongoing research efforts to 

demonstrate a renewed perspective regarding the benefits of pavement markings and, where 

information is available, describe the benefits of various aspects of pavement markings. This 

paper presents areas where conclusive findings are available, and describes areas where findings 

are available but show inconsistent and sometimes conflicting results. 
Carlson, Park, and Andersen Page 3 of 21 

INTRODUCTION 

Pavement markings play one of the most important safety functions on our roads. They are 

widely accepted as being beneficial to drivers in that they communicate the intended travel path 

for short-range operations and the roadway alignment for long-range delineation. To ensure 

consistent application of pavement markings, their characteristics and warranting criteria are 

described in the Manual on Uniform Traffic Control Devices (MUTCD) (1), setting national 

standards on their application. 

Despite the national pavement marking standards described in the MUTCD, according to 

a recent American Association of State Highway and Transportation Officials (AASHTO) report, 

every 21 minutes a highway death occurs as a result of a lane departure. In total, that is over 

25,000 fatalities per year, or almost 60 percent of the nation’s highway fatalities. AASHTO has 

developed a Strategic Highway Safety Plan that is designed to reduce these numbers (2). The 

very first objective of the AASHTO Safety Plan is to keep vehicles in their lanes and on the road. 

The AASHTO Safety Plan includes a list of 22 goals to reduce highway fatalities. Various 

states around the country that have implemented the AASHTO Safety Plan have reported 

successes. . For instance, for the last three years, the Missouri Department of Transportation has 

focused on lane departure countermeasures. They have implemented the following 

countermeasures, which have led to a 25 percent reduction in lane departure fatalities from 2005 

to 2007: 

 edge lines and centerlines on all major highways, as well as minor highways with a 

history of crashes; 

 6-inch pavement marking edge lines and skip lines on all major highways; 

 4-foot shoulders on major highways; 

 guardrail and median barriers on all major highways; and 

 signing improvements. 

AASHTO’s first objective—keeping drivers on the road—appears simple enough. 

However, the safety potential of the objective is largely unknown. Surprisingly, there is an 

apparent lack of information concerning the most effective manner for keeping drivers on the 

road. Obviously, pavement markings are a big part of the equation. Although other safety 

treatments can also be used to keep drivers on the road, this paper is exclusively dedicated to 

pavement markings and their potential contribution towards increasing highway safety. 

ANNUAL PAVEMENT MARKING EXPENDITURES 

The science and effort dedicated to pavement markings can sometimes be overlooked. Perhaps 

this is a function of pavement marking unit costs, typically presented in cents per foot on the 

order of $0.10 to $0.25 per foot for conventional markings. However, when each marking on a 

highway and each mile of a highway are added up, the annual cost of pavement markings in the 

United States can be surprising. In an effort to estimate the annual costs, several sources of state 

agency information were combined to develop an estimated annual cost of pavement markings. 

The estimate is based on data from 18 states making up 45 percent of the state-maintained 

highway miles in the United States (3). Extrapolating the average cost per mile for the 

remaining 32 states produced a total annual pavement marking estimate of $911 million in 2007. 

However, this does not include local roads, toll authorities, or private roads and other facilities 

such as parking lots and airports. Nationwide, local roads account for about 75 percent of the 

nation’s highways and roads, or 2.93 million miles (of which about 1.65 million are paved) 

(4, 5). While many of these roads are probably not marked (there are no data at this level), there 
Carlson, Park, and Andersen Page 4 of 21 

is undoubtedly a substantial proportion that are marked. Given the miles of local roads and other 

facilities that use pavement markings, the annual state pavement marking expenditure was 

doubled and rounded, resulting in a nationwide annual pavement marking expenditure of 

approximately $2 billion in 2007. 

BENEFITS OF PAVEMENT MARKINGS 

Despite these annual expenditures, there is a general void in terms of a consolidated effort that 

attempts to quantify proven benefits of pavement markings. Over the years, many research 

projects have focused on specific elements of pavement markings. This paper discusses and 

references early landmark studies, but an emphasis has been placed on some of the more recent 

studies because significant strides have been made to identify pavement marking benefits. Many 

of these recent studies have been the beneficiary of advanced technologies that allow for 

innovative research methodologies. When combined with lessons learned from previous 

research, the most recent research offers new insights into the benefits of pavement markings 

that were previously undetectable. This paper was developed to bring together many of the 

recent and ongoing research efforts to demonstrate a renewed perspective regarding the benefits 

of pavement markings and, where information is available, describe the benefits of various 

aspects of pavement markings. This paper presents areas where conclusive findings are available, 

and describes areas where findings are available but show inconsistent and sometimes conflicting 

results. 

Ideally, this paper would focus exclusively on crash studies and cost-effectiveness 

studies. As described earlier, however, there is not an exhaustive amount of safety-related 

information on pavement markings. In lieu of safety data, other measures of effectiveness have 

been used to assess the benefits of pavement markings. This paper describes four common 

measures of pavement marking performance: safety studies, subjective evaluations, vehicle 

operational studies, and visibility-related studies. Uncommon or unique measures of 

performance are also described. 

PAVEMENT MARKING SAFETY STUDIES 

Many agencies are experimenting with enhanced pavement markings to reduce crashes and/or 

crash rates (i.e., adding markings to rural two-lane highways, adding wider edge lines, installing 

specially designed wet markings, etc.). Much of this emphasis has resulted from national 

programs such as AASHTO’s Safety Plan as described earlier. Other factors, such as increased 

emphasis on accommodating older drivers, have also inspired agencies to evaluate their marking 

programs. 

Some studies have suggested that the use of markings plays a role in the reduction of 

specific crash types under certain conditions (6, 7, 8). Run-off-road and opposite-direction 

crashes are generally overrepresented on our nation’s highways, especially on horizontal curves 

and at night, when fatal crashes are three to four times more likely to occur. In addition, due to 

visual and cognitive deficiencies, older and impaired drivers are especially susceptible to these 

types of crashes. Therefore, crash types that are most likely affected by added markings or 

enhanced markings (added width or more retroreflectivity) are run-off-road and oppositedirection crashes that occur at night, occur on curves, and involve drivers with reduced visual or 

cognitive capabilities (e.g., older drivers or impaired drivers). 
Carlson, Park, and Andersen Page 5 of 21 

Early Pavement Marking Safety Studies 

The earliest research shows consensus that edge line markings provide crash reductions versus 

no markings at all. For instance, in 1957 a study was initiated to install edge lines on rural twolane highways that were at least 20 feet wide (9). A before-after crash study showed a 19 percent 

reduction in crashes after the installation of the edge lines. In addition, edge lines resulted in a 

37 percent reduction in fatalities and injuries, a 63 percent reduction in crashes at access points 

such as intersections and driveways, and a 35 percent reduction in nighttime crashes. Similarly, 

another study initiated in 1959 showed that adding edge lines on rural two-lane highways 20 to 

26 feet wide and with a minimum average daily traffic (ADT) of 1,000 vehicles per day (vpd) 

resulted in a 78 percent reduction in fatalities and a 46 percent decrease in the number of crashes 

at access points (10). 

Probably one of the most robust studies to date concerning the safety benefits of adding 

pavement markings (edge lines in this case) was conceived from the Highway Safety Act of 

1973, which established specific highway safety improvement programs including a pavement 

marking demonstration program that provided 100 percent federal funding for pavement 

markings on all highways excluding the Interstate Highway System (11). The Surface 

Transportation Assistance Act of 1978 continued funding for the program through fiscal year 

1981. 

Although 38 states participated in the demonstration program effort, data from only six 

states met the minimum criteria for a focused study on pavement marking benefits (resulting in 

225 study sites). The minimum criteria for the study sites were that they had to be on two-lane 

highway sections at least 5 miles in length, have a pavement width of at least 16 feet, have a 

speed limit of at least 40 mph, and have no other safety improvements except adding pavement 

markings. The statistical approach used daytime crashes as a control mechanism for regression 

to the mean. Property damage only (PDO) crashes were not used, and fatal and injury crashes 

were combined. 

Overall, there was a statistically significant 12 percent decrease in nighttime crashes. 

Adding edge lines resulted in a statistically significant 16 percent decrease in nighttime crashes 

and a statistically significant 33 percent decrease in low-visibility nighttime crashes. 

The results also showed that adding centerlines and edge lines, and adding edge lines to 

roadways that previously only had centerlines, was most effective on roadways in mountainous 

and rolling terrain. The reduction in both nighttime and low-visibility nighttime crashes was 

statistically significant for both mountainous and rolling terrain. 

When considering pavement width, several insightful findings appeared. For instance, 

22-foot pavements exhibited a 36 percent reduction in nighttime crash rates and a 52 percent 

reduction in low-visibility nighttime crashes (when edge lines were added to existing centerlines 

or both centerlines and edge lines were added). For the same group of roadways and for 20-foot 

pavements, there was a statistically significant 13 percent decrease in nighttime crashes and a 

statistically significant 23 percent decrease in low-visibility nighttime crashes. For pavement 

widths of 18 feet or less, there was a statistically significantly 46 percent decrease in lowvisibility nighttime crashes. 

The report shows that adding edge lines to existing two-lane roadways with centerlines is 

a cost-effective crash-reducing treatment. A detailed example of North Dakota’s edge line 

program shows a benefit-cost (B/C) ratio of 23:1, despite an increase in PDO crashes. 
Carlson, Park, and Andersen Page 6 of 21 

More Recent Pavement Marking Safety Studies 

Much has changed since the first pavement marking studies, including vehicle design, vehicle 

speeds, and traffic volumes. A more recent study, and one of the most often cited pavement 

marking safety studies, was published by Miller in 1991 (12). Using crash statistics and cost 

estimates from that time, Miller determined that even on rural two-lane roads with an ADT as 

low as 500 vpd, edge lines yield a B/C ratio of 17:1. On average, Miller showed a B/C ratio of 

60:1, noting that the B/C ratio increases with traffic volumes and the urban ratio is twice the rural 

ratio. Miller further concluded that edge lines would be justified on two-lane rural roadways if 

an average of one non-intersection crash occurs annually every 15.5 miles. 

 Miller included a meta-analysis of studies with pavement marking safety numbers. He 

found, using studies deemed credible, an average crash reduction of 21 percent that could be 

attributed to pavement markings. One of the reports he reviewed was by Bali et al. (13), who 

examined delineation treatments on rural two-lane highways. This was a 10-state study 

including more than 500 sites. Their study found that adding edge lines and centerlines reduced 

crashes by 36 percent. Adding edge lines to existing centerlines reduced crashes by 8 percent. 

Using the Bali et al. data, Miller produced a B/C ratio for adding edge lines to rural two-lane 

highways as a function of ADT (see Figure 1). 

 

0

10

20

30

40

50

60

70

80

90

100

0 500 1000 1500 2000 2500

ADT

B/C Ratio 

FIGURE 1 Benefit-Cost Ratio for Adding Edge Lines on Two-Lane Highways. 

Even more recently, several meta-analysis efforts have focused on estimating crash 

reduction factors expected for specific countermeasures. These documents include 

comprehensive literature reviews for various pavement marking applications by factors such as 
Carlson, Park, and Andersen Page 7 of 21 

crash type, crash severity, and lane volume (14, 15). A summary of crash reduction factors for 

various pavement marking countermeasures is shown below. 

Countermeasure Crash Reduction Factor 

 Install lane lines to multilane urban roads 18 

 Install centerlines –1 to 36 

 Install centerlines and edge lines –3 to 24 

 Install edge lines 4 to 66 

 

Safety of Wider Pavement Markings 

Naïve before-after crash studies conducted in Virginia and New Mexico in 1987 and 1988 

suggest that wider lines have no safety benefit in terms of reducing crashes (6, 16). However, 

these studies were hampered by insufficient data and lack of experimental control. In an ongoing 

Federal Highway Administration (FHWA) study, commenced in 2006, researchers are taking a 

much more extensive look at the safety of wider pavement markings (17). As part of the current 

study, a nationwide survey was conducted to identify states that have wider pavement markings 

(wider than 4 inches) on all or some of their highways. For those states using wider pavement 

markings, follow-up phone surveys were used to determine if: 

 the locations (by route number and linear reference) could be determined; 

 the use was extensive on roadway segments (i.e., not small spot treatments); 

 the date of installation was known; and 

 sufficient crash, traffic, and roadway data existed. 

The convergence of all the necessary criteria was rare, but three states were identified as 

having the required information—Michigan, Illinois, and Kansas. To date, the researchers have 

focused their efforts on rural two-lane highways in Illinois and Michigan. The total numbers of 

crashes by severity along with single-vehicle and opposite-direction crashes have been 

disaggregated by time of day, driver age, and weather. The widespread use of wider lines in 

these states minimizes the concern of selection bias or regression to the mean. 

In Illinois, data screening reduced the rural two-lane data set to 3,973 segments 

(1,817 miles) consisting of 3,224 segments (1,511 miles) with 4-inch edge lines and 

749 segments (306 miles) with 5-inch edge lines. 

TABLE 1 shows the estimates of the negative binomial regression model coefficients. 

The regression coefficient for edge line width was negative and statistically significant at  = 

0.05, which indicates a positive safety effect of wider edge lines (i.e., a smaller number of 

crashes is associated with wider edge lines). It can also be observed that the signs of the 

coefficients for lane width, shoulder width, log of annual average daily traffic (AADT), and 

presence of horizontal curve (whenever they are statistically significant) are consistent with 

intuition. 

TABLE 1 Estimates of Regression Coefficients of the Negative Binomial Regression Model 

Applied to Illinois Data from 3,973 Segments (1,817 Miles) Aggregated for 6 Years (2001-

2006) 

Variable Total 

Crashes 

Fatal 

Injury 

PDO Day Night Daytime 

Fatal Injury 

Nighttime 

Fatal Injury 

Intercept –5.0743 –5.9166 –5.5362 –7.0307 –4.8645 –7.0871 –6.1145 

Edge line width –0.0403 –0.3295 0.0326 –0.1995 0.0164 –0.3986 –0.2021 

Lane width –0.0771 –0.0966 –0.0733 –0.1090 –0.0580 –0.1120 –0.0720 
Carlson, Park, and Andersen Page 8 of 21 

Shoulder width –0.0121 –0.0339 –0.0073 –0.0320 –0.0014 –0.0391 –0.0316 

Log AADT 0.8489 0.9607 0.8269 1.1263 0.6651 1.1064 0.7453 

Curve presence 0.3146 0.6294 0.2038 0.3156 0.3375 0.3910 0.9120 

Dispersion 0.4238 0.5681 0.4446 0.5793 0.4133 0.8003 0.3184 

Pearson chisquare/DF 1.2993 1.2655 1.2287 1.4470 1.1219 1.3075 1.0695 

Variable Wet Wet Night Single 

Vehicle 

Single 

Vehicle 

Wet 

Older 

Driver 

Opposite 

Direction 

Fixed Object 

Intercept –7.7794 –7.5721 –3.5669 –5.7371 –7.0303 –14.7968 –4.6039 

Edge line width –0.2539 –0.1727 –0.0044 –0.2196 –0.1127 0.2422 –0.2865 

Lane width –0.0608 –0.0270 –0.0511 –0.0146 –0.0657 –0.1174 –0.0528 

Shoulder width –0.0192 0.0015 –0.0072 –0.0149 –0.0167 –0.0202 –0.0655 

Log AADT 0.9893 0.7668 0.5547 0.6005 0.9307 1.5208 0.6926 

Curve presence 0.4410 0.5484 0.4165 0.5715 0.1958 0.6133 0.7616 

Dispersion 0.7240 0.6887 0.4068 0.7235 0.5613 0.4919 0.5084 

Pearson chisquare/DF 1.1055 1.0854 1.1337 1.0966 1.2856 1.2123 1.2565 

Note: Significant (at  =0.05) effects are shown in bold. 

For Illinois, raised reflective pavement markings (RRPMs) are used statewide, and 

rumble strips are used on interstates statewide. It needs to be noted, however, that the 

information on additional delineation and guidance measures (other than RRPMs and rumble 

strips) and on the roadway curvature was not available and could not be incorporated into the 

analysis. Therefore, the above observations are based on the assumption that the effects of the 

variables not in the database, such as those additional delineation/guidance measures and the 

roadway curvature, are the same (or averaged out) for the segments with and without wider edge 

lines. 

In Michigan, before-after evaluations were conducted with 3 years (2001~2003) of before 

and 2 years (2005~2006) of after data obtained from 386 rural two-lane segments corresponding 

to 1,223 miles of rural two-lane roadways. Although regression-to-the-mean bias is not expected 

to be present (because wider lines were installed statewide in 2004), the empirical Bayes beforeafter evaluations (see, e.g., Hauer [18]) were employed to account for the remaining sources of 

bias such as differences between before and after study periods in traffic volumes, weather, 

vehicle fleet, driver characteristics, economic conditions, reporting practice, etc. 

The empirical Bayes before-after evaluations (using the Illinois segments with 4-inch 

edge lines as the reference sites) resulted in the following crash reduction estimates: total 

(5.8 percent), fatal and injury (24.6 percent), PDO (3.9 percent), daytime (10.9 percent), 

nighttime (3.6 percent), daytime fatal and injury (28.7 percent), nighttime fatal and injury 

(39.5 percent), wet (30.9 percent), wet night (33.2 percent), single vehicle (1 percent), single 

vehicle wet (27.6 percent), single vehicle night (0.9 percent), and opposite direction 

(39.3 percent). All of these crash reduction estimates but nighttime, single-vehicle, and singlevehicle night crashes, were statistically significant at the 95 percent level. The researchers are 

finalizing their rural two-lane analyses with the addition of data from the Kansas Department of 

Transportation. 

SUBJECTIVE EVALUATIONS 

Opinions of the driving public have been used by transportation agencies to evaluate or score the 

agency’s performance and, in some cases, are used to assist in policy decisions. Subjective 
Carlson, Park, and Andersen Page 9 of 21 

evaluations can serve as an indicator of customer desire, but the results are not always tied to 

improvements in safety or what the drivers actually need to drive safely. 

A public opinion survey published by the South Dakota Department of Transportation in 

1997 shows that “keeping stripes visible” was the third-highest ranked attribute out of 21 for 

resource allocation (money and services) as rated by both 768 members of the driving public and 

32 state legislators (19). A follow-up public opinion survey in 1999 showed that 81 percent of 

the 734 respondents felt that poor pavement markings would “somewhat interfere” or “very 

likely interfere” with safe travel (20). 

The American Association of Retired Persons (AARP) had 18 of their instructors drive a 

test course in both daylight and darkness. The drivers were interviewed, and 94 percent of the 

respondents said that 8-inch edge lines affect the way they drive, especially as an aid to staying 

on the road and in their lane (21). Research by Ohme (22) reported that drivers participating in a 

field detection distance evaluation generally judged wider markings as more favorable than 4-

inch markings. Similar results were observed by Pietrucha et al. (23) in simulator evaluations of 

8-inch versus 4-inch edge lines. However, the researchers in both cases found that perceived 

quality and brightness of markings did not correlate well with objective end-detection 

performance for markings of different widths.

There have been a number of publications that document what can be considered 

minimum retroreflectivity levels as judged by nighttime drivers operating vehicles in a range of 

conditions. These studies are subjective in nature, but their results provide a reasonable sense of 

what drivers think they need to drive safely at night. Note, however, that the participants in these 

research efforts, or any typical nighttime driver, might not know what they really need from a 

pavement marking to drive safely. Despite this caveat, the recommendations for minimum 

retroreflectivity levels, based on driver preference (shown in TABLE 2) are generally consistent 

with results ranging from 80 to 130 mcd/m2

/lx. (24, 25, 26, 27, 28). 
Carlson, Park, and Andersen Page 10 of 21 

TABLE 2 Minimum and Desired Retroreflectivity Levels 

Year of Research 

(Reference)

General Minimum 

Recommendation 

(mcd/m2

/lx)

General Desired 

Recommendation 

(mcd/m2/lx)

1986 (24) 100 300-400 

1991 (25) 93 Not applicable 

1996 (26) 121 Not applicable 

1998 (27) 80-120 200 

2002 (28) 130 Not applicable 

While several studies have evaluated the public perception of pavement marking 

brightness, there have been no documented efforts describing how well department of 

transportation (DOT) visual assessments correlate to measured retroreflectivity or how well DOT 

personnel are able to subjectively estimate retroreflectivity. A nearly completed Texas 

Department of Transportation (TxDOT)-sponsored study is currently evaluating the accuracy of 

DOT personnel’s visual assessment of pavement marking retroreflectivity under a variety of 

typical nighttime roadway conditions (29). 

A driving course was selected that had markings of varying retroreflectivity levels (80 to 

700 mcd/m2/lx) and the following roadway characteristics: 

 pavement type (new asphalt, aged asphalt, concrete, or seal coat); 

 lighting conditions (no fixed lighting or fixed lighting); and 

 speed (≤40 mph, 45 to 55 mph, or ≥60 mph). 

State DOT personnel drove the course and were asked to visually assess the 

retroreflectivity. Days before the visual assessment, the researchers thoroughly measured 

marking retroreflectivity. The researchers are comparing the visual assessment against the 

measured retroreflectivity levels to determine if visual nighttime inspection is a viable method to 

evaluate pavement marking retroreflectivity. The researchers are also assessing if the varying 

conditions have any influence on the ability to consistently rate different sections. 

EFFECT OF PAVEMENT MARKINGS ON VEHICLE OPERATIONS 

Measures such as speed and lateral position in the travel lane are surrogate measures for safety 

that are commonly used in the absence of crash data. The following subsections describe recent 

research that relates to the effect of pavement markings on lateral position and speed. 

Vehicle Speed 

While there have been a number of studies that used vehicle speed as a measure of pavement 

marking performance, most show no significant effect in absolute speed difference or, perhaps 

more importantly, speed variance (which is strongly correlated with crash rates [30, 31]) . For 

instance, in 2004 van Driel et al. (32) performed a meta-analysis of vehicle operating speeds 

based on edge line presence. The range of reported before-after results was –3 mph (reduction in 

mean speed) to +8.1 mph. An overall increase in mean speed after installing edge lines on 

roadways that previously only had a centerline was less than 0.5 mph. The authors came to the 

conclusion that the net speed effect was essentially zero. 

In 2005, researchers from Louisiana reported on a before-after study of adding edge lines 

to narrow two-lane highways (with pavement widths of 20 to 22 feet) (33). Conclusively, the 
Carlson, Park, and Andersen Page 11 of 21 

researchers found that the addition of an edge line on narrow two-lane highways did not impact 

vehicle speeds, day or night. 

A recent study performed by Donnell et al. (34) for FHWA focused on the effectiveness 

of pavement marking delineation on curves to induce consistency in vehicle speed and lateral 

position based on a nighttime driving experiment. Based on the results of the present nighttime 

driving experiment, the use of brighter or wider pavement markings does not improve speed 

consistency between an approach tangent and the midpoint of a horizontal curve. 

Tsyganov et al. (35) conducted a before-after study on rural two-lane highways where 

edge line markings were added. The highways had lane widths of 9, 10, and 11 feet. The 

researchers discovered that there were no significant differences in vehicle speeds before and 

after adding edge lines to the narrow highways. They also learned that there were no statistical 

differences in vehicle speeds when considering daytime versus nighttime conditions. The 

researchers’ findings consistently showed that speeds slightly increased in all conditions after 

edge lines were applied, but the differences were not deemed statistically significant. They also 

showed that their absolute speed standard deviations were all less than 1 mph. 

Many experts believe that drivers reduce speeds based solely upon their perceived risk. 

For instance, if drivers perceive sharp curves, narrow lanes or shoulders, steep roadside dropoffs, low side friction, etc., they will lower their speeds accordingly. 

Lateral Vehicle Position 

While research shows that the variance of vehicle lateral placement is strongly correlated 

with crash rates, there have been inconsistent findings related to the effect of pavement markings 

(36, 37). A meta-analysis of lateral vehicle position was performed by van Driel et al. (32). 

Based on research conducted in the United States, the change in mean lateral position after 

installing edge lines on roadways that previously only had a centerline was approximately 

0.5 inches toward the centerline. The range of reported before-after results was a –10.5-inch shift 

(toward the centerline) to a +14-inch shift away from the centerline. The authors came to the 

conclusion that the net lane position effect was essentially zero. 

The work previously described by Donnell et al. (34) resulted in findings that indicate 

there is little evidence to show that enhanced pavement markings change the way in which 

motorists transition from a tangent into a curve. As such, the authors concluded that use of 

enhanced pavement markings does not improve driver lane position differential between an 

approach tangent and the midpoint of a horizontal curve. 

On the other hand, Cottrell (38) compared the lateral vehicle position of vehicles using 4- 

and 8-inch-wide edge lines. The results indicated that lateral vehicle position variance was 

unchanged at locations with a 4-inch edge line but was lowered during both day and night for the 

8-inch edge line condition. 

The research conducted in Louisiana also investigated lateral placement as a function of 

adding edge lines to rural two-lane highways (33). Their before-after measurements show that 

edge lines help drivers confine their traveling path, particularly at night. They found that with 

edge lines, centralization of vehicles’ position is more apparent at nighttime and drivers 

generally position their vehicle away from the edge line, irrespective of the roadway alignment. 

Tsyganov et al. (35) also evaluated lateral placement after adding edge lines to narrow 

two-lane highways. They discovered a reduction in vehicle lateral placement variability, 

meaning vehicles were more consistently following a specific path. The exact location of that 

path depended on the overall lane width. For the 9-foot lane width, the vehicle path shifted 
Carlson, Park, and Andersen Page 12 of 21 

closer to the newly installed edge line, especially in the curve sections. For 10-foot lane widths, 

there were no consistent changes noted. However, for the 11-foot lane width highways, the 

majority of the drivers moved closer to the centerline, especially on the curve sections. 

However, all the changes were subtle. 

MEASURES OF PAVEMENT MARKING VISIBILITY 

In this paper, visibility evaluations include research directed toward the identification of 

correlation rates between pavement marking visibility (measured in terms of retroreflectivity) 

and crashes, and research evaluating the detection of pavement markings with various 

characteristics and properties. Detection distances are thought to be a surrogate for crash data in 

that longer detection distances have a positive effect on vehicle-control measures and, 

consequently, crashes. Because of this, incremental visibility improvements provided by 

pavement markings have been viewed as a proxy for improved roadway safety, although no 

direct link has been established.

Studies of Visibility in Terms of Retroreflectivity and Crashes 

Recently, there have been several attempts to statistically link pavement marking retroreflectivity 

levels to crash rates. A significant challenge has been that pavement marking retroreflectivity 

levels are dynamic in that they continuously change. Attempts to model pavement marking 

retroreflectivity degradation curves have not been widely successful (39, 40). While there is 

some predictability to pavement marking retroreflectivity (it is generally accepted that ADT is a 

significant predictor variable), it can change unpredictably and substantially as a function of 

frequency and intensity of rain (to clean markings), quality of installation, or even the condition 

of the pavement. Therefore, it is difficult to know the retroreflectivity levels of the pavement 

markings at the exact time and location of each crash. While crash data are available, 

researchers have had to make assumptions regarding the retroreflectivity levels for their 

analyses. Some researchers model retroreflectivity using various sources of measured data, 

while others make assumptions about the retroreflectivity without measurements. This section of 

the paper describes attempts to statistically link pavement marking retroreflectivity levels to 

crash rates. 

In 2006, researchers in New Zealand studied the safety impacts of brighter pavement 

markings and concluded that there was a not a conclusive improvement in safety (41). In 1997, 

New Zealand implemented a minimum maintained retroreflectivity policy of 70 mcd/m2

/lx for 

their state system. Using a before-after approach, the authors compared the crash rates before 

the change in policy. They assumed that markings were brighter during the after period. It 

should also be pointed out that, in New Zealand, all state roadways are delineated as a function 

of traffic volume. As volumes increase, they progressively apply the following 

treatments: delineators, centerlines, edge lines, and then RRPMs. Therefore, roadways with 

centerlines had delineators too. Previous research in the United States has shown that 

supplemental delineation treatments, such as delineators or RRPMs, overpower the potential 

effect of pavement markings (42). 

Also in 2006, the results of a National Cooperative Highway Research Program

(NCHRP) study were published with the following conclusions: “...the difference in safety 

between new markings and old markings during non-daylight conditions on non-intersection 

locations is approximately zero” (43). While the study incorporated large amounts of crash data 

and utilized the latest statistical techniques, there were significant limitations to the study. For 
Carlson, Park, and Andersen Page 13 of 21 

instance, the research only included crashes from California and modeled retroreflectivity (no 

measurements were made). While the study included efforts to overcome the possible 

limitations in modeling retroreflectivity, these efforts presuppose that markings in California 

never reach a value where there is an adverse impact on safety. The pavement marking 

maintenance policy of California is such that they restripe their higher-volume highways up to 

three times a year with paint, or every two years with thermoplastic markings. As a result, there 

is only the occasional roadway with retroreflectivity levels below 100 mcd/m2

/lx. 

Overlooking the concerns regarding the modeled retroreflectivity levels, perhaps even 

more concerning is the binning of the modeled retroreflectivity levels. The binning thresholds 

were derived linearly, which by itself is a limitation since the performance of retroreflectivity has 

been repeatedly shown to be best modeled logarithmically rather than linearly (47, 48). In 

addition, the authors binned the modeled retroreflectivity data such that the lowest bins for the 

edge lines included retroreflectivity levels from 21 to 183 mcd/m2

/lx, thus including both 

inadequate levels and near-desired levels in the same bin (see TABLE 2). Eight additional bins 

included retroreflectivity levels up to 413 mcd/m2/lx. Therefore, all binning used in the analyses 

included levels deemed to be acceptable or at least above minimum retroreflectivity levels. 

Combined, these limitations and concerns seriously challenge the quoted concluding remarks 

shown above. 

In 2007, researchers reported results from an effort to develop a statistical association 

between measured pavement marking retroreflectivity and traffic crash frequency (44). The 

results suggest that increased levels of the average pavement marking retroreflectivity on multilane highways may be associated with lower expected target crash frequencies; however, the 

association is small in magnitude and not statistically significant. On two-lane highways, the 

association between pavement marking retroreflectivity and crash frequency is larger in 

magnitude and marginally significant. While this study used measured retroreflectivity levels 

(recorded once per year), it should be noted that all the retroreflectivity data were well above 

what might be considered minimum levels, and even near what might be considered desired 

levels (all data were above 100 mcd/m2/lx with an overall average of 240 mcd/m2/lx). These 

researchers are continuing to evaluate their data using innovative techniques such as modeling 

retroreflectivity using neural networking techniques. 

In 2008, a similar effort was reported that included 3 years of measured retroreflectivity 

(measured once per period) in Iowa (45). These data were analyzed along with crash records 

from the same year. The distributions and models of the entire database, and a subset including 

only two-lane highways, did not show that pavement marking retroreflectivity correlated to crash 

probability. When truncating the data to only records with retroreflectivity values ≤ 200 

mcd/m2/lx, a statistically significant relationship was determined. However, the correlation was 

small. This research is also being continued using retroreflectivity thresholds near the generally 

accepted minimum levels of 100 mcd/m2

/lx. 

Studies of Visibility in Terms of Detection Distances 

Pavement marking detection distances are usually measured with two different techniques. In a 

static setup, the driver counts the number of skip lines visible. In a dynamic setup, where the 

research participant is driving the vehicle, the driver is tasked with detecting either the beginning 

or end of a long line, an isolated skip line (52), or a discontinuity such as a taper (46). The 

results are reported in maximum nighttime detection distances. These studies are usually 

conducted with pavement markings of various retroreflectivity levels (measured dry or wet), of 
Carlson, Park, and Andersen Page 14 of 21 

different widths, and from different vehicles (in consideration of their size and headlamp type). 

The studies have repeatedly shown that pavement marking detection distances are correlated to 

retroreflectivity in a logarithmic fashion (47, 48). 

While the use of wider pavement markings continues to grow across the United States 

(49) and research results are looking favorable in terms of the impact on safety, the results of 

studies based on maximum detection distances of pavement marking widths are inconclusive. 

On one hand, a number of research efforts show increased visibility for wider lines (22, 50, 51), 

while on the other hand, research findings also show that there are no consistent statistical or 

practical differences (23, 52). An empirical study has shown that theoretical calculations of 

marking detection distance as a function of marking width are invalid, and more work is needed 

to develop mathematical relationships between marking width and detection distances (53). 

OTHER PAVEMENT MARKING STUDIES 

While this paper includes some of the most common and often cited measures of pavement 

marking performance, it is not intended to be 100 percent comprehensive. Other techniques have 

been used successfully to evaluate pavement markings and measure their benefits. One approach 

is based on psycho-physiology measures that account for the workload of the driver. Another 

approach monitors drivers’ eye movements to identify how drivers use pavement markings 

during their driving tasks. Examples of each of these techniques are described below. 

Driver Workload Measures 

Tsyganov et al. (35) conducted a unique study on rural two-lane highways where edge line 

markings were added. The highways had lane widths of 9, 10, and 11 feet. The researchers 

tested driver workload before and after edge lines were installed. For workload, the researchers 

monitored heart rate. They found that the addition of edge lines on narrow two-lane highways 

decreased workload at nighttime conditions for both free driving conditions (i.e., no oncoming 

vehicles) and meetings with oncoming traffic. For instance, the addition of edge lines showed an 

average 15 percent decrease in the total time when participants were deemed to be experiencing 

high mental workload rates during nighttime driving conditions. On average, the mean nighttime 

mental workload rate was reduced by 12 percent after adding edge lines. Other means of 

measuring driver workload have been used in the past as well, including galvanic skin response, 

steering fluctuations, accelerator and brake pedal activations, etc. 

Driver Eye-Tracking Measures 

As described above, visibility-related research provides inconclusive results in terms of increased 

detection distances provided by wider markings. However, an ongoing safety study is 

demonstrating that wider markings can reduce crashes on rural two-lane highways. 

Pavement markings provide two primary functions: previewing the roadway alignment 

(using far or foveal vision) and maintaining lane position (using near or peripheral vision). 

Foveal detection tasks have been thoroughly studied to no avail (i.e., inconsistent findings) in 

terms of identifying benefits of pavement marking width. Therefore, it seems reasonable to 

postulate that peripheral visibility measures may provide a stronger visibility measure of 

effectiveness in terms of identifying benefits of wider pavement markings. In fact, McKnight 

(54) conducted research showing that intermediate crash measures, such as lane positioning 

attention management (where drivers focus their attention), are related to peripheral vision. The 
Carlson, Park, and Andersen Page 15 of 21 

researchers showed that major improvements in lane keeping are associated with wider pavement 

markings (studied under low contrast levels). 

TxDOT is sponsoring research aimed at determining how wider pavement markings may 

assist the driver in lane keeping tasks by allowing the foveal focus (i.e., driver attention) to be 

available more often for other driving tasks because of the enhanced information available 

through peripheral vision. A hypothesis to be tested is that the peripheral vision system, at least 

when constrained to a particular boundary and known scene, such as the view through the 

windshield during nighttime driving, is capable of target recognition using very low cognitive 

power. 

The premise is that a driver’s central vision, which is only directed to short-distance 

pavement marking viewing when needed (i.e., low-visibility conditions or unexpected targets), 

would be more available for other driving tasks such as scanning the roadside, reading signs, 

checking mirrors, etc. Undoubtedly, there are endless targets recognized in the periphery that 

somehow are processed as insignificant and therefore cause no need for our central vision focus. 

If wider markings can reduce the amount of time the central focus is needed on short-range 

pavement markings, then the potential benefits of wider markings could be realized. Drivers 

could then manage their foveal vision on other driving tasks as noted above, therefore ultimately 

providing a safer driving environment. 

The research requires drivers to navigate a serpentine test track in an instrumented 

vehicle during nighttime conditions while wearing state-of-the-art eye-tracking equipment. In 

stage one, the drivers’ view is controlled so that they see the course under two conditions. The 

first condition is with their standard low-beam headlamps. The second condition is similar 

except that the near-field illumination is removed (i.e., occluded). Comparison of lateral 

placement, speed selection, and eye-tracking data will allow the researchers to test the strength of 

the premise regarding how drivers rely on pavement markings using peripheral vision. 

Assuming this premise holds true and is validated through the testing described above, 

the researchers will repeat the experimental plan in three phases (stage two). The differences 

between each phase will be the pavement marking retroreflectivity and the pavement marking 

width. Using this approach, it is envisioned that the research could develop relationships 

demonstrating how the use of wider lines permits drivers to manage their vision system in a more 

effective manner, which would lead to a reduction in crashes. This research has the potential for 

a significant breakthrough in terms of quantifying the benefits of wider markings, particularly 

demonstrating how drivers use pavement markings at night to maintain their lane position. 

FINDINGS 

Despite a national standard on the uniform application of centerlines, lane lines, and edge lines—

which is designed to promote highway safety and efficiency—every 21 minutes a highway death 

occurs from a lane departure. While there is a national effort to keep drivers on the road, and 

pavement marking is one potential countermeasure (with an estimated annual expenditure in the 

United States of $2 billion), there is a need for a consolidated effort to bring together recent and 

ongoing research findings demonstrating a renewed perspective on the benefits of pavement 

markings. 

Crashes 

Almost all the recent crash research has been geared toward adding edge lines to highways. 

Recent crash studies as well as those more than a half century old have conclusively shown that 
Carlson, Park, and Andersen Page 16 of 21 

adding edge lines to rural two-lane highways can reduce crashes and fatalities. Some of the 

findings demonstrate that these benefits can be achieved with narrow pavement widths (18 feet 

or less) and low ADTs (as low as 1,000 vpd). The benefits have been shown to be statistically 

significant in areas of all terrain types, and in all locations during nighttime conditions and 

nighttime low-visibility conditions. 

In terms of vehicle speeds and lateral placements, there appears to be either no real 

impacts or, at most, only subtle impacts as a result of adding edge line markings. This includes 

narrow two-lane highways and day and night conditions. 

In a recent study, driver workload was reduced after edge lines were added to narrow 

two-lane highways. 

Wide Markings 

Earlier crash studies conducted on wider pavement markings were inconclusive, showing no 

particular benefit. However, current research using the latest statistical analysis techniques is 

showing the potential benefit of wider pavement markings on rural two-lane highways. For 

instance, edge line width has been found to statistically lower nighttime fatal and injury crashes 

in an ongoing analysis of two state’s data, which is particularly useful since the nighttime crash 

rates is approximately three times higher than the daytime crash rate. 

These new safety findings, though, are not supported by the latest visibility research, 

which has shown inconsistent findings related to increased detection distances from wider 

markings. The expectations are high for ongoing research to demonstrate how wider markings 

can lower crash rates. Using state-of-the-art eye-tracking equipment in an instrumented vehicle, 

researchers are currently evaluating how drivers use markings through both the foveal and 

peripheral vision system. 

Retroreflectivity 

While the FHWA works to develop minimum maintained retroreflectivity levels for pavement 

markings (55), several agencies have conducted subjective evaluations of their roads and 

pavement markings to identify what drivers think they need. Having highly visible pavement 

markings is a high-ranking desire among the public. It also appears that the public prefers to 

have their markings maintained to at least 80 to 130 mcd/m2

/lx. 

Research is currently underway to assess whether DOT personnel can adequately judge 

marking retroreflectivity during nighttime visual inspections. This will be a key element of 

managing retroreflectivity in terms of maintaining adequate levels of retroreflectivity for safe 

nighttime driving. 

The correlation between retroreflectivity and crashes has been a topic of recent research. 

Several efforts have been completed to identify a statistical correlation, but no conclusive 

evidence has yet to be generated. Each effort has been unique and innovative in terms of the 

study approach, but they either used assumed or modeled retroreflectivity data, or 

retroreflectivity data that were measured but much higher than what has been judged to be a 

preferred minimum, 80 to 130 mcd/m2

/lx. Continued research using measured retroreflectivity 

data and advanced analysis techniques is generating promise in terms of identifying the elusive 

correlation between retroreflectivity and crashes. 

DISCUSSION 
Carlson, Park, and Andersen Page 17 of 21 

It is evident from this paper that the arena of pavement marking research is active and delivering 

findings demonstrating the effects of pavement markings and their characteristics. Despite the 

new and exciting findings, it also appears obvious that more work is needed and opportunities 

exist to develop safety-based policies and performance-based specifications. 

For instance, there is an excellent opportunity to investigate how the MUTCD pavement 

marking warrants could be modified based on safety-supported criteria. Speed is not currently 

considered in the criteria. What if the policy on pavement marking applications was tied to 

minimum retroreflectivity levels in a way that provides a synchronized approach so that higherspeed roadways have higher requirements of retroreflectivity (to provide drivers with adequate 

preview times from low-speed to high-speed roadways)? 

Another area of needed research is thorough analyses of crashes by key factors such as 

pavement marking presence, lane widths, ADT, functional classification, curve presence, and 

volume. This should include state and local roadways. The results of thorough analyses could 

be used to support changes to the MUTCD policies that would provide safety-supported policies 

for when to apply pavement markings. 

Continued work is needed to develop a correlation between retroreflectivity and safety. 

Although existing work is ongoing, the task is challenging. A key component of having a 

successful effort is having rich data sources. In this case, there needs to be a rich data source for 

both crashes and measured pavement marking retroreflectivity. The most challenging item is 

having retroreflectivity data that are reliable and represent the condition of the pavement 

marking during crash periods. 

Another area of research that is potentially rich with information is further study of how 

drivers use pavement markings during daytime and nighttime conditions. More information is 

needed to better understand how driving behavior shifts during low-visibility conditions, when 

negotiating horizontal curves, or when oncoming traffic approaches at night. 

There are many advances underway. Pavement marking technologies are producing 

more durable markings, brighter markings, and markings that continue to retroreflect even during 

rainy conditions. Agencies are continuing to use pavement markings on rumble strips for added 

visibility and durability. Many agencies are developing successful pavement marking 

management tools that include innovative performance measures. The specifications for 

pavement markings are also evolving to accommodate new technologies and innovative 

pavement marking management practices. These efforts, and others, have been shown to be 

effective. As noted earlier, the Missouri Department of Transportation has seen a 25 percent 

reduction in lane departure crashes since implementing policies to help keep drivers on the road. 

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