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       The agency has decided to redo more than 50,000 miles of the state’s highway system over the next decade, installing new 6-inch-wide medians.
       The new 6-inch-wide reflective road markings were first installed in 2017 as part of the I-80 “Across the Top” project in Sacramento. Crews completed a series of improvements along a 10-mile stretch of I-80. The $136 million project was an ideal place to test the new markings, as the highway is a major thoroughfare into the heavily traveled capital. Caltrans took the opportunity to test the materials’ durability and evaluate their longevity and effectiveness.
       Due to the reflective properties of glass beads, light penetrates them and is reflected back to the driver, allowing him to better see road markings on the road.
       Following this success, Caltrans has decided to redesign more than 50,000 miles of lanes on the state highway system over the next decade, replacing the long-standing standard 4-inch-wide lanes with new road dividers. The 6-inch-wide lanes are made of either tape or thermoplastic with glass beads. Both the thermoplastic and the tape used to delineate the lanes contain tiny glass beads that increase reflectivity, especially when illuminated by car headlights or during rain. The materials have proven to be very durable and are expected to maintain minimal reflectivity even with prolonged, heavy wear. Not all areas of the state will see the new marking material, however, as it will not be used on roads above 3,000 feet above sea level where snow removal equipment is used. Excavators used to remove snow and ice will also remove the thermoplastic strips, so Caltrans repair crews will continue to repaint the lines as damage occurs.
       Gone with the new markings are the raised, non-reflective road signs called Botts dots, named after the California Department of Transportation scientist who invented them in 1953. Gone with the new markings are the small bumps that were commonly used as lane dividers.
       Caltrans has pioneered the use of durable pavement marking materials by developing warranty performance, permanent tapes, methyl methacrylate (MMA) and thermoplastic materials to improve nighttime visibility in wet conditions. The Pavement Marking Material Selection Guide is designed to assist design engineers in selecting pavement marking materials for the state highway system. The pavement marking material selection process is based on the expected remaining service life of the pavement, pavement type, climate conditions, location and expected performance characteristics of the pavement marking material.
       The California Department of Transportation (Caltrans) recognizes the potential economic benefits and safety improvements of lane expansion and system-wide warranted marking. On January 4, 2017, the Federal Highway Administration (FHWA) published in the Federal Register a Notice of Proposed Revision (SNPA) to the Manual on Uniform Traffic Control Devices (MUTCD) that specifies a minimum level of residual retroreflectivity for markings. Based on this document, Caltrans is developing a policy that will require a minimum residual retroreflectivity level of 100 mcd/m²/ls in its durable marking performance specifications.
       According to technical literature and agency feedback, wider lane markings can improve driving conditions such as long-range nighttime detection, peripheral vision stimulation, lane orientation, and driver comfort. Lane markings are an important means of visual communication with drivers, informing them that they can safely use the road. The new 6-inch (15 cm) lane markings, with their wider and brighter outlines, are expected to improve safety for older drivers and truck drivers and provide effective control in adverse conditions such as rain. According to the Federal Highway Administration (FHWA) Aging Roadway Design Guide, increasing the width of longitudinal travel lines benefits older drivers and improves the visibility of lane markings for all road users, providing better orientation on the road, especially during periods of poor visibility such as rain.
       In inclement weather and at night, when overhead lighting may be poor or even absent, road markings must convey information. Road markings, 6 inches (15 cm) wide, provide a valuable, continuous flow of road information that road signs or traffic lights cannot provide. They alert drivers to changes in the road and help them stay in their lane without taking their eyes off the road. Road markings are used to separate oncoming traffic and guide vehicles to the correct location on the road. When maneuvering, drivers use road markings to guide them along the road.
       Wider, sharper lines and higher reflectivity can increase the visibility of the lines and potentially improve the driver’s ability to perceive them in peripheral vision. These improvements can help improve lane keeping performance and positively impact safety.
       A study by the Texas A&M Transportation Institute (TTI) titled “Evaluating the Effectiveness of Wider Edge Lines” found that wider road markings (edge ​​lines) on the shoulders of roads can reduce crashes and fatalities. The study analyzed Federal Highway Administration (FHWA) data for Kansas, Michigan, and Illinois. All of the data supported the effectiveness of wider edge lines.
       When replacing old standard 4-inch (10 cm) wide pavement markings with new standard markings, the old markings are first removed from the road, then cleaned and the new markings are applied using a primer and a striping machine. Caltrans workers then add small glass beads. The paint dries without smearing. It usually takes 10 minutes for the paint to dry completely.
       Thirty-three states use wide lanes (5 to 8 inches) and have no documented safety issues. The California Department of Transportation has used wider lanes in bike lanes, high-occupancy vehicle (HOV)/carpool lanes, and spur lanes for years and has no documented safety issues.
       In addition to requiring wider, more durable traffic lanes, Caltrans also develops guidelines and procedures for maintaining traffic lanes on state highways. Caltrans’s Maintenance Division is developing guidelines for methods to monitor and maintain the durability and reflectivity of traffic lanes.
       In fiscal year 2017-18, Caltrans completed 35 lane marking contracts totaling 17,500 miles (27,500 km) for a total value of $210 million. These projects use lane marking warranties if the pavement life is greater than five years. For pavements with a service life of five years or less, other durable materials are used. Thermoplastics, MMA, and two-component paints are used for edge markings. Recessed markings are used for projects located above 3,000 feet (910 m).
       All 27,000 miles of California’s freight highways — Interstates 5, 10, 15, and 80 — will be rebuilt over the next few years. The rebuild of California’s entire highway system is expected to occur within a decade, with funding in part provided by Senate Bill 1 (SB 1), the Road Repair and Accountability Act of 2017. Signed into law on April 28, 2017, SB 1 invests $54 billion over the next decade to repair roads, highways, and bridges in communities across California. The funds will be split equally between state and local governments. This will address the backlog of repairs and upgrades while ensuring a smoother, more resilient transportation network for the future. California’s state-supported transportation infrastructure will receive about half of SB 1’s funding, about $26 billion, while the other half will go to local roads, transit agencies, and expanding California’s growing network of sidewalks and bike paths. Each year, new funding will be used to address deferred maintenance needs, with about $1.8 billion going to maintaining and repairing the state’s road network. Caltrans has committed to repairing or replacing 17,000 miles of pavement by 2027. While crews repair and replace pavement on state roads, Caltrans is re-marking the roads to meet new 6-inch (15 cm) width standards. These 6-inch-wide reflective markings not only improve safety on state roads, but also meet the demands of new technology.
       Caltrans is actively preparing for future innovations and technologies and is actively engaging with transportation industry leaders. Caltrans has consulted with two autonomous vehicle giants, Tesla and Google, on replacing road markings. Autonomous vehicles are equipped with sensor technology that can read road markings. Cameras can recognize edge lines, lane lines, center lines, and other markings. Wider longitudinal markings and high-performance markings improve camera detection rates and facilitate the advancement of autonomous vehicles on California highways. Compared to 4-inch-wide markings, 6-inch-wide reflective markings will provide better road guidance for autonomous vehicles.
       Caltrans’ goal is to make California’s interstates safer and more convenient for drivers. In the past, fog and heavy rain have made it difficult for drivers to see road markings, so Caltrans hopes that 6-inch (15 cm) wide reflective markings will improve visibility. Using new materials that are more reflective, the 6-inch (15 cm) white reflective markings will reflect off the glass beads and provide safe road lighting for drivers traveling in California.