Engineers in Portland, Ore., turned to a big rig recently for help testing their light rail train.

A highly customized Western Star 4900 SA was used to haul a 100-ton Metropolitan Area Express (MAX) train to test track and power line clearances. Steel wheels guided the truck on rails while the tandem tires stayed on the track to drive the truck.

"The 4900 SA is one of our most versatile models," said Cary Gatzke, Western Star's director of engineering. "The 4900 SA is adaptable to a wide range of commercial vehicle jobs and we are very pleased the truck was able to meet the Interstate MAX challenge. We're especially happy that a Western Star was able to show off its capabilities in Portland, Ore., where these trucks are built."

The 4900 SA line of vehicles feature a single steer front axle range of up to 20,000 pounds and tandem steer axles up to 40,000 pounds. The rear axle capacity ranges up to 58,000 pounds. A full range of manual, automated and automatic transmissions also are available. Engines vary in horsepower. All 4900 SA Line vehicles come standard with a high-visibility hood.

The 4900 SA truck used in the Interstate MAX line test is owned by TriMet. TriMet provides public transit for much of three counties in the Portland metropolitan area. TriMet operates the 38-mile MAX light rail line, 100 bus routes and service for seniors and people with disabilities.

The $350 million MAX light rail extension is expected to open this fall.