Alaska DOT testing differential speed limits to improve passing lanes on Seward Highway

Updated Jul 14, 2016

Alaskan-road-Better-RoadsThe Alaska Department of Transportation & Public Facilities (ADOT&PF) is running a differential speed limit pilot program on five miles of Seward Highway in an effort to improve passing lane traffic. The left lane will remain at the normal speed limit of 65 miles per hour and the right lane’s speed limit will be reduced to 55.

ADOT&PF used driving simulators to study various “alternatives” to improve its passing lanes, and the differential speed limit option proved the most effective.

“With a lower posted speed limit in the right (slow) lane, passing speeds can be reduced while allowing more vehicles to pass within designated passing lanes,” the department says. “Additionally, aggressive behaviors can be reduced when drivers feel like they have time to pass. Efficient use of passing lanes is critical in summer months when traffic is at its peak and recreational drivers are on the road.”

Seward Highway’s passing lanes in the pilot program area (Mile 60-65) have an average daily traffic count of 9,000 vehicles, but peak at 20,000 during a few days in July, according to ADOT&PF.