All-Weather Pavement Marking for Work Zones: Field Evaluation in North Carolina and Ohio

TEMPORARY WET-WEATHER PAVEMENT MARKINGS FOR WORK ZONES, PHASE II FINAL REPORT

PUBLICATION NO. FHWA-HIF-13-004
May 2013

Notice

This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document.

The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers' names appear in this report only because they are considered essential to the objective of the document.

Quality Assurance Statement

The Federal Highway Administration (FHWA) provides high-quality information to serve Government, industry, and the public in a manner that promotes public understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its information. FHWA periodically reviews quality issues and adjusts its programs and processes to ensure continuous quality improvement.

Technical Report Documentation Page

1. Report No. FHWA-HIF-13-004	2. Government Accession No.			3. Recipient's Catalog No.
4. Title and Subtitle Temporary Wet-Weather Pavement Markings for Work Zones, Phase II: All-Weather Pavement Marking for Work Zones, Field Evaluation in North Carolina and Ohio				5. Report Date May 2013
				6. Performing Organization Code
7. Author(s) C.M. Cunningham, J.E. Hummer, J. Chang, D. Katz, C.L. Vaughan, D.J. Findley, B.J. Schroeder, and D. McAvoy				8. Performing Organization Report No.
9. Performing Organization Name and Address Institute for Transportation Research and Education North Carolina State University Centennial Campus Box 8601 Raleigh, NC 27695				10. Work Unit No. (TRAIS)
				11. Contract or Grant No. DTFH61-08-G-00001
12. Sponsoring Agency Name and Address Federal Highway Administration Highways for LIFE Program – HIHL-1 1200 New Jersey Avenue, SE Washington, D.C. 20590				13. Type of Report and Period Covered Final Report, November 2007-April 2013
				14. Sponsoring Agency Code
15. Supplementary Notes
16. Abstract To address the problem of seemingly invisible pavement markings under nighttime, rainy conditions, 3M developed “All-Weather Paint” (AWP), which uses highly retroreflective elements in combination with latex-based pavement marking installed by highway agencies. Whereas standard pavement markings using waterborne pavement marking and glass beads become harder to see in the rain, the AWP performed well during closed-circuit field tests. Researchers at North Carolina State University and Ohio University teamed up to conduct tests in active highway work zones. The team defined four measures of effectiveness (MOE) in an attempt to quantify safety performance when comparing the AWP to standard pavement marking materials under real-world driving conditions: retroreflectivity, vehicle travel speed, rate of lane encroachments, and linear lane displacement. Data collection procedures for each MOE are systematically outlined throughout the report. From the results, the study concluded the following: (1) Retroreflectivity values were confirmed to be higher for AWP when compared to standard pavement markings. However, the AWP retroreflectivity values were inconsistent, likely because of the variation of application methods by pavement marking contractors. (2) Speed was used as a surrogate MOE to evaluate safety performance. It was not clear if an increase or decrease in speed has a positive effect on safety. Results showed that speed generally increased as drivers exited work zone lane shifts for all marking types; however, no consistent finding was noted between the two marking systems in similar curves. (3) The findings for lane encroachments varied throughout the sites. While the first site studied indicated that more lane encroachments occurred at standard pavement marking crossovers, a more robust study at a second site found the results to be statistically insignificant. (4) When assessing lateral lane placement, researchers found statistically significant but varied results. More often than not, motorists maintain safer lane placements when traveling along the AWP delineated lanes. This report documents Phase II of this project. The Phase I report is available on the FHWA website at: Final Report Phase 1 – Temporary Wet-Weather Pavement Markings for Work Zones.
17. Key Words Retroreflectivity, pavement markings, work zone safety			18. Distribution Statement No restrictions. This document is available to the public through the National Technical Information Service, Springfield, VA 22161.
19. Security Classification (of this report) Unclassified		20. Security Classification (of this page) Unclassified			21. No. of Pages 63	22. Price

SI* (Modern Metric) Conversion Factors

APPROXIMATE CONVERSIONS TO SI UNITS					APPROXIMATE CONVERSIONS FROM SI UNITS
Symbol	When You Know	Multiply By	To Find	Symbol	Symbol	When You Know	Multiply By	To Find	Symbol
LENGTH					LENGTH
in	inches	25.4	millimeters	mm	mm	millimeters	0.039	inches	in
ft	feet	0.305	meters	m	m	meters	3.28	feet	ft
yd	yards	0.914	meters	m	m	meters	1.09	yards	yd
mi	miles	1.61	kilometers	km	km	kilometers	0.621	miles	mi
AREA					AREA
in2	square inches	645.2	square millimeters	mm2	mm2	square millimeters	0.0016	square inches	in2
ft2	square feet	0.093	square meters	m2	m2	square meters	10.764	square feet	ft2
yd2	square yards	0.836	square meters	m2	m2	square meters	1.195	square yards	yd2
ac	acres	0.405	hectares	ha	ha	hectares	2.47	acres	ac2
mi2	square miles	2.59	square kilometers	km2	km2	square kilometers	0.386	square miles	mi2
VOLUME					VOLUME
fl oz	fluid ounces	29.57	milliliters	ml	mL	milliliters	0.034	fluid ounces	fl oz
gal	gallons	3.785	liters	L	L	liters	0.264	gallons	gal
ft3	cubic feet	0.028	cubic meters	m3	m3	cubic meters	35.314	cubic feet	ft3
yd3	cubic yards	0.765	cubic meters	m3	m3	cubic meters	1.307	cubic yard	yd3
NOTE: Volumes greater than 1000 l shall be shown in m3
MASS					MASS
oz	ounces	28.35	grams	g	g	grams	0.035	ounces	oz
lb	pounds	0.454	kilograms	kg	kg	kilograms	2.202	pounds	lb
T	short tons (2000 lb)	0.907	megagrams	Mg	Mg (or "t")	megagrams (or "metric ton")	1.103	short tons (2000 lb)	T
TEMPERATURE (exact degrees)					TEMPERATURE (exact degrees)
°F	Fahrenheit	5(F–32)/9 or (F–32)/1.8	Celcius	°C	°C	Celsius	1.8C +32	Fahrenheit	°F
ILLUMINATION					ILLUMINATION
fc	foot–candles	10.76	lux	lx	lx	lux	0.0929	foot–candles	fc
fl	foot–Lamberts	3.426	candela/m2	cd/m2	cd/m2	candela/m2	0.2919	foot–Lamberts	fl
FORCE and PRESSURE or STRESS					FORCE and PRESSURE or STRESS
lbf	pounds	4.45	newtons	N	N	newtons	0.225	poundforce	lbf
lbf/in2	pound per square inch	6.89	kilopascals	kPa	kPa	kilopascals	0.145	poundforce per square inch	lbf/in2

*SI is the symbol for the International System of Units. Appropriate rounding should be made to comply with Section 4 of ASTM E380. (Revised March 2003)

Table of Contents

• INTRODUCTION
• LITERATURE REVIEW
  • Rain and Night Conditions Nationwide
  • Adverse Weather Crashes
  • Safety in Work Zones
  • Pavement Markings
  • Measures of Effectiveness
  • Retroreflectivity and Safety
• SITE SELECTION
  • Site Selection Criteria
  • Site Descriptions
  • Discussion of Potential for Data Collection
  • Retroreflectivity
  • Data Collection
  • Analysis Methodology
  • Results
  • Conclusions and Recommendations
  • Speeds
  • Data Collection Methods
  • Analysis Methodology
  • Results
  • Conclusions and Recommendations
• LANE ENCROACHMENTS
  • Data Collection
  • Statistical Analysis of Lane Encroachments
  • Conclusion and Recommendations
• LATERAL LANE PLACEMENT
  • Data Collection
  • Analysis Methodology
  • Results
  • Conclusions
  • Overall Conclusions
• REFERENCES

List of Figures

• Figure 1. Chart. 2008 mean total precipitation.⁽¹⁾
• Figure 2. Graph. Safety in work zones.⁽⁵⁾
• Figure 3. Photos. Wet weather comparison of standard pavement marking (left) and the AWP (right) pavement markings.
• Figure 4. Photos. Comparison between standard pavement marking (left) and the AWP marking with microcrystalline ceramic beads (right).
• Figure 5. Graph. Minimum pavement marking retroreflectivity requirements as a function of speed.⁽¹⁹⁾
• Figure 6. Photo. I-85 crossover locations.
• Figure 7. Photos. I-85 southern crossover during daytime and nighttime.
• Figure 8. Photo. Aerial view of northern crossover. Southbound traffic shifts to northbound side divided by a jersey barrier.
• Figure 9. Photo. Aerial view of southern crossover. Southbound traffic shifts back to normal operation.
• Figure 10. Photo. US-15/501 crossover locations.
• Figure 11. Photo. US-15/501 southern crossover – standard pavement marking and the AWP study site.
• Figure 12. Photo. Nighttime camera views of US-15/501 northern crossover.
• Figure 13. Photo. US-421 crossover locations.
• Figure 14. Photos. Four curves at the US-421 test site.
• Figure 15. Photo. US-32/33/50 work zones.
• Figure 16. Photos. The AWP (left) and standard pavement marking (right) work zones on eastbound US-32/33/50 during the day.
• Figure 17. Photos. The AWP (left) and standard pavement marking (right) work zones on eastbound US-32/33/50 at night.
• Figure 18. Photo. I-90 crossover locations.
• Figure 19. Photo. AWP treatment location on I-90.
• Figure 20. Photo. Standard pavement marking treatment location on I-90.
• Figure 21. Photos. View of the AWP (left) and standard pavement marking (right) double-lane crossover.
• Figure 22. Diagram. Retroreflectance measurement fields.
• Figure 23. Photo. Internal view of sensor.
• Figure 24. Photo. Sensor on mounting base.
• Figure 25. Graphs. US-32/33/50 speed results by location in work zone.
• Figure 26. Graphs. US-32/33/50 lane placement results.
• Figure 27. Graph. I-90 lane placement results.

List of Tables

• Table 1. Nighttime visibility of painted and thermoplastic centerline and edge line markings under low-beam illumination.⁽¹⁶⁾
• Table 2. Field test site descriptions.
• Table 3. Average monthly rainfall totals (inches).⁽²²⁾
• Table 4. Average available time for nighttime data collection (hh:mm).⁽²²⁾
• Table 5. Retroreflectivity sample size obtained at each of the four sites studied.
• Table 6. List of retroreflectivity samples at each site.
• Table 7. Summary of statistics for retroreflectivity readings at all test sites.
• Table 8. Summary of statistics for speeds.
• Table 9. US-32/33/50 speed ANOVA results.
• Table 10. I-90 speed analysis ANOVA results.
• Table 11. Chi-square results for US-15/501 lane encroachments.
• Table 12. US-421 lane encroachment statistics.
• Table 13. Summary of statistics for lateral lane placement.
• Table 14. US-32/33/50 lane placement ANOVA results.
• Table 15. I-90 lane placement ANOVA results.

List of Abbreviations

AADT	Average Annual Daily Traffic
ANOVA	Analysis of Variance
AWP	All-Weather Paint
CCTV	Closed-Circuit Television
DOT	Department of Transportation
FHWA	Federal Highway Administration
LIDAR	Light Detection and Ranging
MOE	Measure of Effectiveness
NOAA	National Oceanic and Atmospheric Administration
RI	Refractive Index
RPM	Raised Pavement Marker
TIP	Transportation Improvement Project

Executive Summary

Traffic crashes cause tens of thousands of deaths every year; thus, highway safety is at the forefront of the decision making process of transportation improvement projects. Traffic-related fatalities and severe crashes top the list and are immediate areas of concern to transportation policy and decision makers. Aside from mistakes made by drivers, the conditions of the road and environment often factor in the motorist decision process. Factors including, but not limited to, weather, lighting, and surface deterioration are examples often considered in the condition of the national highway system. Pavement markings are the focus of this research effort—specifically, improving their retroreflectivity under nighttime rainy conditions, which often hinder motorists’ ability to drive safely, especially in work zones, where quick decisions are often a life-or-death situation. Decreased visibility of lane delineation and lack of situational awareness make navigation through complex work zones potentially unsafe for drivers.

To address the problem of poor visibility of pavement markings under nighttime, rainy conditions, 3M developed “All-Weather Paint” (AWP). AWP utilizes highly retroreflective elements in combination with latex-based pavement marking installed by highway agencies. Whereas standard pavement markings become harder to see in the rain, the AWP performed well during closed-circuit field tests.

Researchers at North Carolina State University and Ohio University teamed up to conduct tests in active highway work zones. Five test sites were selected in North Carolina and Ohio. The team defined four measures of effectiveness (MOE) in an attempt to quantify safety performance when comparing the AWP to standard pavement marking under real-world driving conditions: pavement marking retroreflectivity, vehicle travel speed, rate of lane encroachments, and linear lane displacement. Data collection procedures for each MOE are systematically outlined throughout the report. Basic statistical analyses were performed, and the methodologies are stated herein.

From the results, the study concluded the following:

• Retroreflectivity values were confirmed to be higher for AWP when compared to standard pavement markings. However, the AWP retroreflectivity values were inconsistent, which was likely due to the variation of application methods by pavement marking contractors.

• Speed was used as a surrogate MOE to evaluate safety performance. It was not clear if an increase or decrease in speed has a positive effect on safety. Results showed that speed generally increased as drivers exited work zone lane shifts for all pavement marking types; however, no consistent finding was noted between the two marking types in similar curves.

• The findings for lane encroachments varied throughout the sites. While the first site studied indicated that more lane encroachments occurred at standard pavement marking crossovers, the more robust study of the second site found results to be statistically insignificant.

• Finally, when assessing lateral lane placement, researchers found statistically significant but varied results. More often than not, motorists maintain safer lane placements when traveling along the AWP delineated lanes.

In summary, this study shows that AWP provides a low-cost, all-weather marking to improve lane visibility and to enhance safety.

Introduction

Pavement markings are a vital tool for safely navigating our nation’s roads. Pavement markings come in many variations, depending on the application. Many of the pavement markings used today are especially difficult to see in the rain, particularly during nighttime hours. One commonly used pavement marking (herein referred to as “standard pavement marking”) uses a latex paint coupled with 1.5 refractive index glass beads that retroreflect light back to the driver. More times than not, this application method is used in temporary installations such as work zones. However, because the marking is hard to see during nighttime rainy conditions, there is concern that drivers may have lane-keeping issues when navigating through active work zones. This poses a hazard to drivers and increases the risk of crashes. Therefore, most States currently supplement the pavement marking application with raised pavement markers to provide a visual cue to the driver on the location of the lane line.

Funded under the Federal Highway Administration (FHWA) “Highways for LIFE” technology partnerships program, this research project aims to test a variation of the latex-based pavement marking that uses specially designed optical elements for temporary applications such as work zones. Developed by 3M, the “All-Weather Pavement marking” (AWP) consists of a standard pavement marking supplemented with additional optical elements that retroreflect light in rain conditions, greatly increasing visibility during rain events.

Phase I of this study involved testing in a controlled environment. First, 24 pavement marking samples were installed on a test deck in New Orleans, LA, and time-series data regarding their retained retroreflective properties were collected. Three prototype all-weathering markings were identified to carry into the next task, which involved the installation of the pavement markings at the Texas Transportation Institute rain range. In these studies, the AWP and conventional markings demonstrated substantial differences in retroreflectivity; however, these studies were not conducted under real-world driving conditions, and they could not address any issues with contractors applying the markings in a dynamic environment where application time must be considered to keep traffic moving.

To build on the findings of Phase I, the Phase II effort aims to study actual drivers as they navigate through work zones by comparing standard pavement marking to the AWP under daytime, nighttime, and rainy conditions. First, the research team conducted a literature review to learn from previous research in the area of pavement marking studies. Following this effort, they selected field test sites based on a variety of factors, including a minimum of two lanes per direction in the transition zone, no raised pavement markers (RPMs), a minimum speed limit of 45 miles per hour, and no disruption from nearby traffic signals. In total, five sites were chosen, three in North Carolina and two in Ohio. Next, standard pavement marking and the AWP were applied in each of the chosen work zones. The analysis considered four measures of effectiveness (MOE): retroreflectivity, speeds, lane encroachments, and lateral lane placement. Retroreflectivity was utilized to determine differences in pavement marking application across sites and between pavement marking types at the same site. Speed was used to supplement findings from the latter two MOEs since higher or lower speeds could not be correlated to better or worse driving conditions. Last, lane encroachment and lateral lane placement were the primary MOEs used to determine if safety had improved using the new AWP.