Retroreflectivity, which makes pavement markings visible at night, happens when the light from vehicle headlights bounces back toward the driver’s eyes. Visible markings help prevent lane departure crashes. But markings degrade over time due to weather and wear from traffic, so departments of transportation need to keep on top of pavement marking maintenance through regular inspections and replacement of sub-par markings.
Until recently, markings were measured subjectively by just taking a look and rating the condition of the marking. For the past year, however, retroreflectivity has been measured objectively, and data from those measurements is available on UDOT’s Data Portal.
Each spring and fall, employees from UDOT’s Maintenance Planning Division measure the retroreflectivity of markings on a randomly chosen selection of roadway segments, including dashed lane markings and solid lines that mark the edge of the road.
Measurements are taken using a mobile retroreflectometer mounted in a van. The retroreflectometer, shoots a high intensity Laser in a sweeping motion over marked pavement and measures the light that reflects back in milli-candelas per lux per meter squared – a measure of light per unit area.
The data gathered by the measuring effort is compiled and graded from A+ to F – this spring, UDOT got a B. This year’s fall data is in the process of being compiled. The data on UDOT’s Data Portal can be viewed on a map alone or along with other data sets.
Over time, having an objective measurements of pavement retroreflectivity will help support safety by helping to direct funding where improvement is needed.