More than 30 years ago, Congress directed the Federal Highway Administration (FHWA) to develop a standard that agencies could use to determine whether pavement markings needed maintenance.
On August 5, 2022, the Federal Highway Administration published a final rule on minimum reflectivity for road markings that will take effect 30 days later. This final rule was incorporated into the Manual on Uniform Traffic Control Devices (MUTCD), which is recognized as the national standard for traffic control devices on all streets, highways, bike paths, and private roads open to the public.
The final rule was formally incorporated into the 2009 MUTCD, Version 3, and is expected to be incorporated into Version 11 as well. Improving nighttime safety and visibility for drivers is one of the primary reasons for establishing thresholds for the maintenance of reflective road markings.
According to the Federal Highway Administration, the number of traffic fatalities in the United States at night is about three times higher than the number of daytime fatalities. However, the thresholds set by the FHWA in the final rule are not based on improving safety, but rather on the nighttime visibility needs of older drivers.
This theory is relevant to safety, but evidence-based research shows that to improve nighttime safety for all drivers, different reflectivity thresholds should be considered to reduce nighttime crashes.
Although there are exceptions and other factors, the MUTCD’s required minimum reflectivity level is set at 50 mcd/m2/lx (mcd/m2/lx is a measure of how much light is reflected at a given illuminance) for longitudinal markings on roads with speed limits of 35 mph and above.
This applies to both white and yellow vertical markings. For motorways with a speed limit of 70 mph or more, a higher level of 100 mcd/m2/lx is recommended but not required.
These conditions were based on older drivers being able to see nighttime markings within a preview time of about 2.2 seconds. They do not include adverse conditions such as weather, oncoming vehicles, other sources of glare or complex backgrounds.
While the MUTCD minimum reflectivity levels for road markings may provide some relief when continuous lighting is present, they do not provide relief when retroreflective road markings are used.
To better understand the impact of road marking reflectivity on safety, researchers examined the reflectivity of yellow center lines on Michigan highways during nighttime and single-vehicle nighttime collisions.
When the reflectivity of yellow is below 150 mcd/m2/lx, the number of accidents at night increases significantly. The results of the study also show that as the reflectivity of the yellow center line approaches 150 mcd/m2/lx, the expected collision frequency decreases.
A subsequent study used the same data but with more sophisticated analysis methods to establish a safe minimum threshold of 175 mcd/m2/lx for maintaining yellow centre lines on rural two-lane highways.
There are many factors to consider when developing a cost-effective road marking program. For example, establishing initial and maintenance reflectivity levels is only part of the equation. Select the appropriate adhesive (such as paint or thermoplastic) and the right reflective optical beads.
Not all adhesives and optics wear out at the same rate, so measurement marks are also an important factor. Surveying equipment generally falls into two categories: handheld, which often requires lane closures to keep workers safe, and mobile, which keeps vehicles and projects running smoothly.
Road markings have been used on our roads for over 100 years, and they will become even more important as onboard cameras and other sensors enable self-driving cars. Efforts are underway to study how best to prepare and maintain roads for these new technologies, which promise to improve mobility, safety, reduce congestion and save lives.
Post time: Mar-07-2025