More than the Stripes on the Road
A new bypass curves through eastern Mullica Hill, N.J., adding a 1.5 mile stretch to U.S. Rt. 322, a decades old highway that winds its way in South Jersey between the Commodore Barry Bridge and the shore. The multi-year project, designed to relieve congestion and improve safety, connects two parts of Rt. 322 while skirting the center of town.
Where the bypass reconnects with Rt. 322, large letters, arrows and route symbols on the pavement shout: go here to continue east or there to head west. These pavement markings don't work alone\; road signs indicate curves and turn lanes.
These signs little and large, and pavement markings flat and raised, point the way and help drivers follow the route safely. "Pavement markings are essential in providing the driver the information he needs to drive safely," says Jerry Britt, technical service manager, Eastern Region, Ennis Traffic, Wesson, Miss., and chairman of ASTM D01.44 on Traffic Coatings.
Traffic-related agencies and manufacturers, contractors and engineers depend on ASTM International standards that specify, describe and characterize materials for road signs and markings\; these and other ASTM standards, for friction measurement and traffic control data, contribute to safety on the road.
Road signs announce speed limits, curves, intersections, passing or no passing zones, turn lanes, lane merges, lane edges, road work, animal crossings and more. In the United States, the Federal Highway Administration publishes the definitive compilation on the topic, the Manual on Uniform Traffic Control Devices. According to the manual overview, "The use of uniform TCDs (messages, location, size, shapes and colors) helps reduce crashes and congestion, and improves the efficiency of the surface transportation system."1
The MUTCD references national standards for signs and markers, including ASTM D4956, Specification for Retroreflective Sheeting for Traffic Control, a standard that covers white and colored sign material used in many types of signs. "Standards provide useful tools for agencies to ensure the materials they use meet minimum criteria," says Jason Davis, special testing engineer, Louisiana Department of Transportation and Development Materials Laboratory, Baton Rouge, La., and chairman of D04.38 on Highway Traffic Control Materials.
Design engineers and departments of transportation then choose TCD materials with consideration for road use and weather as well as disruption to traffic and road crew safety. A traffic paint might mark a low traveled rural road. And, thermoplastic marking or preformed tape would be a possible choice for roads carrying a high volume of traffic.
To test their sign and marker materials, manufacturers take part in the NTPEP, National Transportation Product Evaluation Program, which is sponsored by the American Association of State Highway and Transportation Officials. Each spring, manufacturers submit samples for test decks for one-, two- or three-year tests. Decks are placed across the United States for the program, and one deck can test 200 similar products side by side. According to the NTPEP summary, ASTM D713, Practice for Conducting Road Service Tests on Fluid Traffic Marking Materials, levels the playing field for measurement.2
D713 describes how to evaluate the wear of paints, thermoplastics, epoxies and polyesters in actual road usage. "D713 cuts across all product lines and it deals with the key elements that relate to field performance of those markings," says Britt. "It is a very important document." He notes that most states are involved in the NTPEP, and manufacturers use the NTPEP reports for research or product approval.
While some sign and marker standards specify materials based on their physical and measured characteristics, a new effort is underway at ASTM to develop a driver-based approach that relies on human factors research by the Texas Transportation Institute in cooperation with the Texas Department of Transportation and FHWA. The research gathered data on legibility and eye-tracking to measure how drivers use signs at night. The research goal: to recommend a performance-based specification based on nighttime driver needs. The revised standard's goal? To approach the topic based on what the drivers need, not what the materials can provide.
Paul Carlson, research engineer at the Texas Transportation Institute in College Station, Texas, who supervised the TTI research, says, "Many agencies are looking for ways to determine which kind of retroreflective sheeting material they should use on their signs. Most, if not all, agencies look to ASTM for help."
In the many times D4956 had been revised since its original publication in 1989, the standard had been more about codifying properties of materials, Davis says. He adds, "we are moving toward a method based on what a driver needs in order to identify and read highway signs under actual road conditions."
ASTM road marking and sign standards address paint and thermoplastics, retroreflection and color. These standards are the responsibility of D01.44 on Traffic Coatings\; D04.38 on Highway Traffic Control Materials and E12.10 on Retroflection. The three regularly meet together and members often participate in two or all three groups.
D01.44 develops test methods, practices and guides for traffic paint, thermoplastic and other road marking materials\; D04.38 focuses on specifications for traffic marking and signing: retroreflective sign sheeting, raised pavement markers and preformed marking tape\; and E12.10 on standard methods, practices and guides that address retroreflective, color and appearance measurement of sign and pavement marking materials.
E12.10 focuses on a property important to standards from both D01.44 and D04.38: retroreflection. The subcommittee studies and describes the geometric and spectral properties of retroreflection, a property that becomes critical after dark to make road signs and markings visible. "If it weren't for that, you may not see the markings at night," Britt says.
"In layman's terms, retroreflection is the scientific term that describes the ability of an object to redirect light back to its source," says Chris Gaudette, manager of specifications and testing for Reflexite, an Orafol Company, Avon, Conn., and chairman of E12.10. That light gathering and reflecting property is typically a result of either glass beads that can be as small as grains of sand or by cube corner microprisms, which may number more than 70,000 per square inch. For a driver, the light from a sign, pavement tape or paint, or marker reflects back to his eyes\; he can then see the information more easily.
For its part, D01.44 provides the methods to test the properties of glass beads such as roundness (D1155) and sieve (size) analysis (D1214)\; both give the user a means to check for compliance with specification requirements that contribute to retroreflection.3 And, E12.10 provides the methods to test the properties of retroreflective materials such as sign sheeting and delineators (E810), and pavement markings under standard conditions of continuous wetting (E2832)\; both give the user a means to check for compliance with retroreflection requirements.4 "By understanding what current materials can do, how they perform, adjustments and designs can be made that make improvements that help the ultimate users, drivers of vehicles," Gaudette says.
Now, this decades-old technology is utilizing new retroreflective optics that are engineered to focus light more efficiently and improve visibility in bad driving conditions. D01.44 is currently working on a standard to evaluate such composite optics: WK35519, Test Method for Evaluation of Retroreflective Composite Optics for Traffic Markings.
Standards also make an impact on road safety in more subtle but important ways. It's here, where the rubber meets the road, that standards from Committee E17 on Vehicle-Pavement Systems help characterize the dynamics of the vehicle-road connection.
"The ability to characterize resistance to skidding in any direction is the most essential thing E17 does for safety," says Kevin McGhee, chairman of E17 and associate principal scientist for the Virginia Department of Transportation, Charlottesville, Va.
Skid resistance has to do with friction, and "friction directly relates to the safety of roads," says E17 member Zoltán Radó, Ph.D., director of the Vehicle Systems and Safety Program at the Pennsylvania Larson Transportation Institute, Pennsylvania State University, University Park, Pa.
The type of road impacts the required level of friction. A high speed road with incoming traffic and intersections - a high risk road - demands more friction. A low speed, straight road requires less friction. In either case, rough, wet or icy pavement reduces friction.
To determine friction, according to Rado, most state departments of transportation look to E274, Test Method for Skid Resistance of Paved Surfaces Using a Full-Scale Tire. E274, one of a family of E17 friction measurement standards, provides measurements representing steady-state friction on a locked test when dragged over a wet pavement. Rado says, "ASTM E274 is by far the most common for measurements in the United States for management of roads and highway." Agencies use these friction measurements to plan road maintenance and improvements.
E17 member Steven Jessberger notes that E17 standards also improve traffic data collection. "E17 has a number of standards that different agencies use to collect traffic data," says Jessberger, transportation specialist, Office of Highway Policy Information, Federal Highway Administration, Washington, D.C. "Traffic data is used as an exposure rate or the denominator for a number of safety-related statistics."
Among E17 data standards, E1957 helps ensure accurate information\; E2467 assists in obtaining data and summary statistics\; E2415 and E2532 guide the installation of data collection devices\; and E1318 helps articulate specifications and criteria to help obtain the best possible WIM systems.5 "The standards provide information to help clearly understand the context they are used in and to communicate effectively what is needed," Jessberger says.
Through these standards, and the data from the thousands of U.S. counting sites, highway officials can make informed decisions about traffic light timing, changes in traffic flow, or perhaps - as with Rt. 322 - building a bypass to relieve congestion and improve safety.
1. U.S. Federal Highway Administration, "Manual on Uniform Traffic Control Devices," http://mutcd.fhwa.dot.gov.
3. D1155, Test Method for Roundness of Glass Spheres\; D1214, Test Method for Sieve Analysis of Glass Spheres.
4. E810, Test Method for Coefficient of Retroreflection of Retroreflective Sheeting Utilizing the Coplanar Geometry\; E2832, Test Method for Measuring the Coefficient of Retroreflected Luminance of Pavement Markings in a Standard Condition of Continuous Wetting (to be available soon).
5. E1957, Practice for Installing Using Pneumatic Tubes with Roadway Traffic Counters and Classifiers\; E2467, Practice for Developing Axle Count Adjustment Factors\; E2415, Practice for Installing Piezoelectric Highway Traffic Sensors\; E2532, Test Methods for Evaluating Performance of Highway Traffic Monitoring Devices\; E1318, Specification for Highway Weigh-in-Motion (WIM) Systems with User Requirements and Test Methods.
An Interview with Aurelio Menéndez, Ph.D., manager for the Latin American and Caribbean transport sector of the World Bank
Through its memorandum of understanding program, ASTM International collaborates with several national standards bodies in countries across Latin America, and longstanding MOU partners reference ASTM standards for road signs, paints and markers, and retroreflectivity. Here, Aurelio Menéndez of the World Bank addresses challenges and initiatives related to road safety.
Other than the need for improving road system conditions and redesigning locations that have higher crash injury and death rates, the main challenges can be divided into three main categories: institutional organization, information and enforcement. In the area of institutional organization, in many Latin American countries there is a lack of clarity in coordinating and assigning responsibilities. This institutional disconnect must be overcome through the creation of a lead government agency responsible for coordinating the efforts of governmental and nongovernmental agencies.
With regard to information, the challenge is in creating a unified database allowing for uniform registration of vehicles and drivers. It is also essential to have information about road safety conditions as well as standardized criteria for assessing risks and obtaining consistent results for effective decision-making. Efforts to establish a regional road safety observatory are an example of work in this area. The International Road Assessment Program tools allow for risk assessment as a proactive method for reducing traffic crash deaths and injury rates when reliable crash data are not available.
Legal frameworks, educational and public awareness campaigns, and technological means and procedures for enforcing traffic laws and aiding victims are still deficient in most Latin American countries. This issue is especially critical in urban areas, where the rate of traffic fatalities is high, mainly affecting the most vulnerable individuals: pedestrians, children and elderly people. Actions aimed at strengthening the professionalization of traffic police, acquiring supporting equipment such as speed-monitoring devices and breathalyzers, distribution of educational material, enhancing accident response systems, publicity campaigns and training exchanges with other countries are examples of low cost measures that can be implemented rapidly.
The primary initiatives are aimed at improving infrastructure, strengthening institutions, creating unified and consistent database systems, and ramping up enforcement. Identification of high risk areas along the road network, their management and maintenance, as well as road sign placement, are elements that have been included in road investment projects across the region.
In addition, establishing a lead agency and an institutional framework that allow for better coordination between agencies involved in road safety issues is a key initiative, along with information exchanges and learning between countries, and the training and professionalization of personnel involved (particularly in education, healthcare and traffic police). Another relevant initiative is the development of uniform driver and vehicle registration systems along with the creation of data repositories (observatories) that allow for reporting and monitoring traffic injury and fatalities statistics in order to identify priorities.
About 1.3 million people die each year as a result of road traffic crashes. That's according to the World Health Organization, which also notes that more than 90 percent of these fatalities occur in low- and middle-income countries, and that nearly half of those deaths are those of pedestrians, cyclist and motorcyclists.
To change this situation, and make the world's roads safer, the United Nations kicked off a campaign last year: the Decade of Action for Road Safety 2011-2020.
"The Decade of Action for Road Safety can help all countries drive along the path to a more secure future," said UN Secretary-General Ban Ki-moon during his address to launch the campaign. He called on groups and individuals everywhere to work to ensure that the decade leads to improvements.
The goal of the Decade of Action is first to stabilize and then to reduce traffic fatalities worldwide, and to encourage actions through improving road safety performance or adopting new safety programs.
The plan for the campaign stresses pillars of activities to take place on the national and local level:
Grants to support road injury prevention programs worldwide are being made through the specially established Road Safety Fund, managed by the FIA Foundation and the World Health Organization. The funds have been made available by companies, governments, philanthropies and the public.