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Project Summary Report 0-4150-S Project 0-4150: Evaluation of Marking Effectiveness Authors: H. Gene Hawkins, Jr., Timothy J. Gates, Elisabeth R. Rose

Pavement Marking Effectiveness and the Pavement Marking Handbook

Pavement markings provide one of the primary means of communicating information to users. Unlike signs and signals, pavement markings are continuous and provide road users with valuable information that helps them properly position the within the travel way. Pavement markings are different from signs in another way: pavement markings are typically manufactured at the location where they are applied instead of being manufactured in a factory and sent to the installation site. As a result, there is the opportunity for greater variability in the performance characteristics of pavement markings. Pavement markings are a primary means of communicating with road users. What We Did … This project evaluated several Pavement Marking all who wished to attend. The key characteristics associated with Conferences many individuals who attended (139) heard presentations from the retroreflective performance of During the first year of the marking experts with other state pavement markings. There were project, The Transportation transportation agencies, the five major activities associated Institute (TTI) hosted two Federal Administration, with this project: pavement marking conferences and industry. Primary issues that to identify and discuss important • conduct of two conferences issues associated with pavement were discussed at the conferences on pavement marking markings in Texas. Key pavement included: thermoplastic application performance, marking stakeholders in Texas, on sealcoat surfaces, striping • evaluation of pavement including many Texas Department inspection, performance and marking retroreflectivity on of Transportation (TxDOT) warranty pavement marking flexible pavements (hot-mix representatives, attended these specifications, and de-bonding of and surface treatments), conferences. The first conference thermoplastic from . was an invitation-only meeting • identification of pavement Markings for Flexible marking use on rigid held in College Station with a pavements (concrete), limited number of individuals Pavements (35) that was intended to identify Providing long-lasting • evaluation of the measurement what the major pavement marking of marking thickness, and thermoplastic pavement markings challenges are. on surface treatment (sealcoat) • development of the Pavement surfaces has become a challenge Marking Handbook. The second conference was held in Austin and was open to for some TxDOT districts. The

Project Summary Report 0-4150-S – 1 – researchers performed a number of agencies. This information was used contribute to the development of tasks to identify effective pavement to develop recommendations for the the handbook. The handbook was marking practices for sealcoat and selection of marking materials on developed to provide a single source hot-mix (HMAC) concrete pavements. of information for anyone involved roadways in Texas. The researchers with pavement markings in Texas. reviewed literature, identified current Measuring Pavement TxDOT and alternative pavement Marking Thickness marking practices, and evaluated What We Found … various pavement marking treatments Pavement marking thickness is The researchers identified numerous in the field. The pavement marking one of the two primary inspection findings that can have an impact on field evaluations were performed measurements made with pavement the quality of pavement markings and on surface treatment and HMAC markings, the other being the resulting effectiveness of those roadways. In most of these field retroreflectivity. Researchers compared markings. evaluations, researchers measured the relative accuracies of thermoplastic thickness measurement with caliper the retroreflectivity of newly applied Pavement Marking Conferences pavement markings and monitored the (common field practice) versus The findings from these conferences performance of the markings over time. needlepoint micrometer (recommended provided the researchers and TxDOT In total, researchers made more than field practice). The main difference staff with much useful information. 9000 retroreflectivity measurements between the two measurement devices Research report 0-4150-3, A at 18 different sites. Figure 1 presents is that the needlepoint micrometer is Summary of Two Pavement Marking a comparison of white edgeline capable of measurement between the Conferences for the Texas Department retroreflectivity over time for various beads, while the caliper is capable of of Transportation, summarizes the marking thicknesses. measuring only to the top-of-bead. The difference between the two activities and findings from the devices is significant because TxDOT conferences. Significant suggestions Markings for Concrete Pavements specifications require contractors to resulting from the conferences include: Several TxDOT districts have achieve minimum thermoplastic • Use 100 mil thermoplastic for all experienced difficulties getting the thickness, not including drop-on beads. standard TxDOT thermoplastic marking longlines on new sealcoat. material to provide adequate durability Pavement Marking Handbook • Experiment with concrete-specific on concrete pavements. In some thermoplastic materials and two- districts, thermoplastic markings have Developing the TxDOT Pavement component materials (e.g., epoxy) an expected life span of a year or less Marking Handbook was the major on concrete pavements. due to de-bonding between the marking implementation effort of the project. Using the information gained from the • Establish consistent statewide and pavement surface. To address these striping inspection practices. items, the researchers synthesized other four activities, TTI researchers information from a number of sources, developed the handbook and refined the • Establish a single statewide including National Transportation content based on input from a panel of retroreflectivity performance Product Evaluation Program (NTPEP) TxDOT staff and selected contractors specification. data and other state transportation that met on several occasions to

Figure 1. Average Retroreflectivity for White Edgeline.

Project Summary Report 0-4150-S – 2 – • Warranty specifications should Measuring Pavement be limited to use only on selected Marking Thickness contracts at the local level. Forty-seven thermoplastic • Monitor marking retroreflectivity pavement marking samples of on a number of different roadway varying thickness and beads were types to determine reasonable taken from striping jobsites statewide retroreflectivity values and and used in the analysis. Research performance periods. report 4150-1, Analysis of TxDOT • Until more experience is obtained, Thickness Measurement Procedures use 250 mcd/m2/lux white and Figure 2. Locations for Measuring for Thermoplastic Pavement Markings, 175 mcd/m2/lux yellow for Marking Thickness. summarizes the findings from the minimum retroreflectivity analysis. The results show that the performance of new markings. • To obtain a more accurate caliper measured an average of representation of long-term 20.5 mil and 16.7 mil thicker than Markings for Flexible Pavements pavement marking performance, the needlepoint micrometer for large The researchers identified few measure retroreflectivity at least one (Type III) and small (Type II) bead shortcomings related to pavement month after striping. samples, respectively. Based on marking practices on HMAC pavement the research findings, the following • To ensure adequate retroreflectivity recommendations were made: surfaces. However, for surface for both directions of traffic, treatments, numerous opportunities for measure retroreflectivity for • Thickness measurements should be improving pavement marking quality centerlines of undivided two-way made with a needlenose micrometer were identified. Research report roadways in both directions. to the top of the thermoplastic. 0-4150-4, Effective Pavement Marking • The use of a caliper to measure Practices for Sealcoat and Hot-Mix Markings for Concrete Pavements thermoplastic thickness is Asphalt Pavements, summarizes discouraged. the results of the evaluations. Based The researchers gathered much on the research findings, numerous useful information regarding pavement • A minimum of three measurements recommendations were developed, marking practices for concrete should be taken. pavements. Research report 4150-2, which include: • The most accurate measurement Effective Pavement Marking Materials method is to measure diagonally • Apply thermoplastic at a minimum and Applications for Portland across the sample (taking at least thickness of 100 mil for all Concrete Roadways, summarizes three measurements per sample). longitudinal pavement markings the findings and recommendations Figure 2 illustrates where the on new surface treatments when no associated with this effort. Based on measurements should be made other durable marking exists. findings, the researchers generated on the sample. • Apply thermoplastic at a maximum a number of recommendations for thickness of 90 mil for all pavement markings on concrete longitudinal pavement markings roadways in Texas, which include: The Researchers on HMAC when no other durable • Use epoxy materials for long-term marking exists. Recommend … applications under the majority of The Pavement Marking Handbook • -based paint may be used on a traffic conditions. serves as the implementation product for new surface treatments in either of the various research activities associated the following situations, but should • Use preformed tape for long-term with this project. It contains guidance, not be used as a permanent marking: applications under very heavy procedures, and recommendations traffic. addressing many different aspects • as temporary pavement marking for up to 6 months, or • Use TxDOT specification of pavement marking selection and thermoplastic only for short-term installation. The objectives of the • as surface primer prior to applications with low to medium Pavement Marking Handbook are to: thermoplastic application. traffic. • harmonize statewide practices, • For better retroreflective • Always ensure that the striping • implement research, and performance of pavement markings surface is clean and dry with no on surface treatments, TxDOT loose material. • provide a single “go-to” resource for Grade 4 sealcoat (smaller striping. • Special concrete thermoplastic diameter) is recommended over The handbook is divided into two TxDOT Grade 3 sealcoat aggregate formulations (not currently included in TxDOT specifications) are main chapters: pavement marking (larger diameter). material selection and pavement suggested for all other thermoplastic • For any pavement surface, use either marking installation and inspection. applications on concrete. TxDOT Type III (larger diameter) Each chapter serves as a stand-alone or TxDOT Type II (smaller document. The handbook provides diameter) glass surface beads with TxDOT engineers and inspectors with thermoplastic to achieve suitable information that will help them better levels of dry-weather retroreflective select pavement marking materials and performance. inspect the installation of markings.

Project Summary Report 0-4150-S – 3 – For More Details . . . The research is documented in four research reports: • 4150-1: Analysis of TxDOT Thickness Measurement Procedures for Thermoplastic Pavement Markings • 4150-2: Effective Pavement Marking Materials and Applications for Concrete Roadways • 0-4150-3: A Summary of Two Pavement Marking Conferences for the Texas Department of Transportation • 0-4150-4: Effective Pavement Marking Practices for Sealcoat and Hot-Mix Asphalt Pavements

Research Supervisor: H. Gene Hawkins, Texas Transportation Institute, [email protected], (979) 845-6004

Researchers: Timothy J. Gates, and Elisabeth R. Rose, Texas Transportation Institute

TxDOT Project Director: Greg Brinkmeyer, TxDOT–Traffic Operations Division, [email protected], (512) 416-3120

To obtain copies of reports, contact Dolores Hott, Texas Transportation Institute, TTI , (979) 845-4853, or e-mail [email protected]. See our online catalog at http://tti.tamu.edu.

The Pavement Marking Handbook (4150-P1) is the implementation product for this research. It is available from the TxDOT Traffic Operations Division. Contact Jeanne Black at (512) 416-3134 to order a copy of the handbook.

TxDOT Implementation Status January 2004

The objective of this research project was to evaluate key aspects of pavement marking effectiveness. One product was required for this project: a pavement marking handbook. The Pavement Marking Handbook can be implemented immediately as it was developed as the single source of information for anyone involved with pavement markings in Texas.

For more information, contact Mr. Wade Odell, P.E., RTI Research Engineer, at (512) 302-2363 or email [email protected].

YOUR INVOLVEMENT IS WELCOME!

Disclaimer This research was performed in cooperation with the Texas Department of Transportation (TxDOT) and the U.S. Department of Transportation, Federal Highway Administration (FHWA). The contents of this report reflect the views of the authors, who are responsible for the facts and accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of TxDOT or the FHWA. This report does not constitute a standard, specification, or regulation, nor is it intended for , bidding, or permit purposes. Trade names were used solely for information and are not for product endorsement.

Project Summary Report 0-4150-S – 4 – TTI.PSR0401.0304.580