AASHTO Journal - Variable Speed Limits Cut Crashes on I-90 in Ohio

A recent report by the Ohio Department of Transportation found that the use of Variable Speed Limits or VSLs along a section of I-90 in Lake County reduced crashes by 35 percent over a seven year period.

[Above photo by Ohio DOT]

The Ohio DOT and Lake County Sheriff’s Department worked together to develop the state’s first VSL section of highway on I-90 in 2017; using digital speed limit signs to reduce the speed limit during adverse weather.

The agency noted in a statement that the Ohio General Assembly also played a key role, modifying the state’s speed limit law to give Ohio DOT the authority to temporarily reduce the statutory speed limit along this specific stretch of I-90.

From 2005 to 2015, the agency said I-90 between State Route or SR 44 and SR 528 suffered a yearly average of 76 reported crashes, with 37 occurring in the winter. Since the implementation of the VSL in 2017, crashes along that stretch of I-90 dropped by over 35 percent to an average of 49 per year, with 21 occurring in the winter.

Additionally, since the VSL system went live in 2017, major crashes have been reduced by more than half, rear-end crashes dropped from 19 to eight, and fatal and injury crashes decreased from 20 to nine crashes per year.

The roadway’s VSL sign system works in coordination with Ohio DOT’s existing Intelligent Transportation System that includes traffic cameras, dynamic message signs, and road weather information stations to monitor visibility and precipitation. All this information is funneled to the agency’s Traffic Management Center or TMC in Columbus.

The TMC, in turn, works with local law enforcement and Ohio DOT managers to make decisions on when to lower speed limits. When the weather changes, the speed limits are reduced in 10 mph increments to warn motorists of hazardous traveling conditions.

For example, a moderate amount of precipitation would warrant a 60-mph speed limit, while blowing and drifting conditions with poor visibility could warrant a 50-mph speed limit. The lowest permitted speed limit is 30 mph, reserved for high-impact events such as a full road closure, Ohio DOT said.