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       But it’s a bit like the situation a driver faces when trying to see road markings in the rain. Lane-keeping/lane-keeping assist vision systems also have to take into account the reduced ability to see road markings on rainy nights as these new high-tech systems help keep vehicles on the road.
       Glass beads have been used for road markings and striping since ancient times. So why do most traditional road markings become harder to see at night when it rains? This is largely due to the optical properties of traditional glass beads. These glass beads fall onto wet road paint when trucks apply markings and stripes. In dry weather, these glass beads are very effective at reflecting headlight energy back to the driver’s eyes, allowing them to keep an eye on the road. However, if the glass beads get wet, their optical properties change, causing the headlight energy to be poorly reflected back to the driver or the machine’s vision system. Until the last decade, there was nothing that could be done about this optical phenomenon caused by rain.
       Over the last decade, the road marking and striping industry has developed special non-glass beads that continue to return headlight energy to the driver in the wet. However, these new non-glass beads for wet conditions are ineffective in dry conditions. As a result, regular glass beads have been mixed with new wet beads to create hybrid beads that, when installed on freshly painted lines, allow drivers and machine vision systems to see road markings from a greater distance in both wet and dry night conditions. However, not all areas of the country experience frequent wet night conditions.
       In areas with unusually wet climates, wet tire formulations could be important to both machine vision users and humans. Wet tire formulations hold promise for reducing serious and fatal crashes caused by run-off roads on rainy nights, but the research has not yet focused on six-month commute conditions in a northern state where rainy nighttime conditions are prevalent. In addition, past studies of wider, brighter road markings have generally failed to challenge the perspectives of machine vision and human drivers. Washington is perhaps one of the best places to demonstrate two different approaches to improving the visibility of all-weather tiered signs. Drivers in western Washington have had to contend with an unusually high number of dark, winter rainy conditions, while eastern Washington beyond the Cascade Mountains has seen mostly dry nighttime conditions. Here, the broader, brighter ideas could be tested in parallel within a single state.
       Human and machine vision systems are always looking for higher contrast in road markings. Higher contrast and visibility provide a greater visual range, which allows more time to make driving decisions. Research collected and summarized by the Washington State Department of Transportation (WSDOT) shows that in drier areas, wider stripes can provide a nearly triple-digit benefit-cost ratio when used in conjunction with road surface, but wider stripes alone still provide a benefit-cost ratio advantage of about 30:1. So, if wider stripes provide increased contrast and safety in dry conditions, imagine the impact of brighter stripes in areas that regularly experience extremely dark and wet conditions.
       California and Oregon are two of the many states that have used these wet, high-performance bead mixes. In fact, local agencies are also using the technology to apply duct tape and plastic striping. Federal Way, Washington will have several new sites this year (2021) that will use wet, high-performance beads on plastic pipes.
       Replacing worn stripes and markings has traditionally been a maintenance function. Any additional costs associated with the extension of weather conditions in which traditional markings and markings are effective will likely place additional pressure on maintenance budgets. Those familiar with the nation’s maintenance budget issues will understand how difficult it is to continue using wet high-performance bead formulations or wider markings under such historical budget constraints. Looking ahead, more funding is needed for protection and maintenance in general, but particularly for road markings and markings, given the potential direct impact on safety and road activity.
       As more resources are invested in improving the safety of road signs and markings, state and local governments will need to determine how best to allocate resources to achieve the greatest benefit for system users, including drivers and ADAS systems. Given the variables involved, this is unlikely to be a one-size-fits-all guide, so it is difficult for a national guide such as the Uniform Traffic Control Devices Manual to provide such targeted improvements. A tailored approach is needed.
       Recognizing federal regulations and the general direction of autonomous vehicle manufacturers to improve the visibility of road lanes and markings to both human and machine vision systems, the Washington State Department of Transportation has developed two concepts for contextual road markings. In rainy western Washington, a high-performance wet-type mix could be installed over traditional 4-inch-wide markings, but with a thicker, more durable coating that could last two seasons in some locations. In the drier eastern part of the state, an approach might be to simply widen the markings to 6 inches, using both traditional water-based paint thickness and a conventional glass bead material.
       The program concept could start with rural roads and then gradually include more systems as the effectiveness of these two context-sensitive approaches is proven.
       Washington has a very strong safety culture and staff with the ability to design research, collect data, and analyze statistically significant results, so we look forward to reading more about how it works.