The Federal Highway Administration’s Office of Operations has published an important benchmarking report on use of performance measures which assesses state DOT adoption and effectiveness of harnessing new techniques and technologies to improve roadway operations impaired by adverse weather conditions.

As FHWA reports, “The impact of weather events on roadway safety and capacity is substantial.” Two measures, in particular, address major concerns for those dedicated to improving winter roadway safety and mobility. They are:

• The percentage of time a roadway meets safety and capacity level of service (LOS) standards during and after weather events (normalized by the frequency/intensity of winter events), and
• The reduction in roadway user costs as measured in traffic delays, crashes, vehicle operating costs, emissions and salt damage attributable to road weather strategies.

As the Salt Institute has argued, FHWA concludes that “national level statistics do no exist yet to directly measure” the goal of measuring safety and LOS/capacity impairment. Nearly a third of agencies (32%) measure “time to wet/bare pavement.” Only 4% measure “percent of time that lanes are open during a weather event, 7% measure “pavement friction,” 11% measure “time to pre-event travel speeds after a weather event” and 18% measure “customer satisfaction with maintenance and recover time.” Another 25% use undefined additional performance indicators.

While performance measures are “in an early phase of deployment,” there is better news in adoption of new operations strategies. New Sensible Salting techniques are being adopted. Road Weather Information Systems (RWIS) is credited with reducing crashes by 17% and anti-icing by 83%, but since the latter figure is equivalent to the 85% crash reduction in using older deicing techniques, the finding hardly represents great progress.

Snow and ice on roadways cause significant service degradation, the report explains, cutting roadway capacity by 25% or more (to say nothing of the number of would-be drivers who abandon planned trips entirely). Free-flow speed declines 19% in snow conditions. Despite this reduced load, weather-impaired roads are the cause of 22% of all injury and fatal traffic crashes, half of them due to slick roadway surface conditions. Overall, weather causes more than 500 million vehicle-hours of delays every year, the report documents. “Most of this estimated delay (90 percent) was due to snow in urban areas.”

Pursuit of road weather performance measures “has enabled and continues to strive for a culture shift among traffic operators to a more proactive weather management approach that in turn will improve safety and capacity,” the report concludes. The federal program is also “undertaking studies relevant to safety, including studies of the microscopic and macroscopic behavior of traffic in inclement weather conditions, weather-sensitive traffic prediction and estimation modeling, and evaluation of the effectiveness and safety implications of road weather advisory and control information.” FHWA is promoting its Maintenance Decision Support System (MDSS) to automate winter operations and participating in the IntelliDrive program to harness new “smart car” technology to improve road weather operations.