Starting later this month, buses in Clark County will make an end-run around traffic on a frequently backed-up highway by driving on the shoulder.

The transit agency C-Tran and the Washington State Department of Transportation will test the concept along State Route 14 in east Vancouver. It's expected to shave 4 to 6 minutes off of some morning bus trips and 2 to 4 minutes from evening commutes once it launches Oct. 23.

The test is the first of its kind in Clark County, and also the first in recent memory in the metro area. But it's an increasingly common approach to getting transit through rush-hour traffic in other parts of the country, including Minnesota, which has 300 miles of bus-only shoulders.

The Washington state transportation department also operates bus-only shoulders on a highway in Bothell.

Signs showing where C-Tran buses may drive on the shoulder went up in July. Elliot Njus/The Oregonian

Six minutes might not seem like a lot on a 25-minute trip that can turn into a 90-minute trip in heavy traffic, but C-Tran spokeswoman Christine Selk said the time saved on each trip will have ripple effects on the following trips and help improve reliability overall.

And it could encourage drivers to consider taking the bus, said Bart Treece, a state transportation department spokesman.

"If you're driving on SR 14 and you see the bus on the shoulder passing you, you might think about your options," Treece said.

The change is also a relatively cheap solution to a growing problem.

The agencies spent about $50,000 to re-stripe SR 14, adding a few more inches to accommodate buses on the shoulder, and to make new signs marking the transit-on-shoulder corridor.

The state transportation department also measured the depth of the pavement on the shoulder to ensure it could stand up to the weight of occasional bus traffic.

The bus-on-shoulder corridor will run between 164th Avenue and Interstate 205 in east Vancouver. Buses that use the stretch of highway include Route 164 (Fisher's Landing Express), Route 65 (Parkrose Regional) and Route 41 (SR 14 Limited).

Buses will only move to the shoulder if traffic is traveling at less than 35 mph. They'll travel no more than 15 mph faster than other traffic, up to 35 mph.

Portland had a short-lived experiment with opening the shoulder of Interstate 84 to buses and carpoolers during rush-hour in the late 1970s.

The resulting carpool lane was removed in 1982, when the freeway was widened in conjunction with the construction of the Banfield light-rail project that would become MAX.

TriMet and the city of Portland are considering bus-on-shoulder corridors alongwith a slate of other potential ways to speed the travel of buses through the city. The agencies haven't identified any potential test site.

Clark County's experiment could also ultimately be short-lived. It's scheduled to run at least 18 months for evaluation, after which it could be continued or expanded to other routes.

The Washington Legislature this year funded a project to add a lane in each direction to the SR 14 bus-on-shoulder corridor. That project is still being designed, and it's not clear if the transit lanes will survive the project.

-- Elliot Njus

enjus@oregonian.com

503-294-5034

@enjus