To Speed or Not To Speed

The Oregon Department of Transportation has installed digital speed limit signs along a 10-mile stretch of U.S. 97 between south Bend and La Pine. The signs can modify speed limits based on road and weather conditions, supported by weather stations that monitor traction, humidity, temperature and visibility. When road conditions are poor the speed limit will decrease, and will rise again once conditions improve.

Seven over-road speed limit signs that cover a 10-mile stretch of U.S. 97 between Bend and La Pine will change the speed limit in real time if there are poor road conditions. Credit: Courtesy of ODOT

“If the road surface gets covered in snow, or it gets slick or visibility goes down, these sensors will tell the speed limit sign to lower the speed,” ODOT spokesperson Kacey Davey said in a video announcing the new signage. “And it is a regulatory speed so if you see that speed goes from 65 to 55, or even lower, that is the actual speed limit.”

ODOT said over 40% of crashes on that section of the highway occurred when a driver was going faster than advisable under road conditions. A study by the U.S. Department of Transportation showed the digital speed limit signs can reduce total crashes on freeways by 34%, rear-ends by 65% and eliminate half of all fatal and injury crashes.

“You’re going to have less impact, you’re going to have more stopping distance, and it could really help reduce the severity and the frequency of crashes,” Davey said.

ODOT turned the signs on on Monday, but it won’t implement a variable speed limit until November. ODOT said it’ll see if the signs are successful in reducing crashes, and if successful will look for more opportunities farther south on U.S. 97.

Highways are the most common place to find variable speed limit signs, but they’re also used in school zones, work zones and transitional zones — where higher speed roads transition into more pedestrian-friendly areas with dramatically lower speeds. Oregon established new criteria for variable speed areas in 2021, but the system has been tested out as far back as 2012 when it installed variable speed limits on the I-5 and I-405 in Portland and on U.S. 26 between Banks and Manning. USDOT estimates the signs could save more than $9 per every $1 spent.

This article appears in Source Weekly October 20, 2022.