The type of commute rail car that travels the 70-mile Sonoma-Marin corridor will set the tone for how the transit system looks and feels.

The selection process, which is now under way, will take almost two years.

?This is crucial to the success of this entire project,? said Carol Russell, a Cloverdale councilwoman and a member of the Sonoma-Marin Area Rail Transit operations committee.

The rail cars envisioned for the tracks between Cloverdale and Larkspur are made by several Canadian, European and Asian companies.

The cars, called ?diesel multiple units,? come in two weights, heavy and light, a measure of crash-worthiness that determines whether they can run alongside freight service and how the station platforms will be built. The SMART trains likely will share the track with freight service.

The trains can be configured to have restrooms, kiosks for food and drink and room for bicycles. At an estimated cost of $88million and with a manufacturing time of two to three years, the vehicles are one of the costlier of SMART?s expenditures.

SMART officials two weeks ago heard presentations by six rail car manufacturers from Canada, Italy, Germany, Switzerland, Spain and Japan. Those companies already have vehicles in operation, and have U.S. manufacturing or assembly plants. The only U.S. manufacturer, Colorado Railcars, initially identified by SMART as its vehicle preference, went out of business in December.

In the next two weeks, the SMART committee and planners will take day trips to gauge operations of systems in San Diego and to Portland, Ore., which are representative of light- and heavy-rail vehicles.

?A lot of the subsequent planning and design work that SMART has to engage in to develop a rail system starts with the vehicle type,? said Lillian Hames, SMART?s executive director.

The North Coast Transit District in San Diego is a light-rail system, using cars produced by Siemens, a German company with an assembly facility in Sacramento.

Light-rail cars are popular in Europe. They are made of lighter materials such as aluminum and fiberglass and have automobile-style crash impact zones built in.

U.S. rail authorities, however, don?t allow them to be on the tracks used the same time as freight trains.

?One of the benefits of the light is it is off-the-shelf technology,? said John Nemeth, SMART?s rail planning manager. ?Most of these companies we are looking at have manufacturing facilities in the U.S. They are already running these, and you know how it performs.?

The Tri-County Metropolitan Transportation District of Oregon recently opened a heavy-rail system using cars made by defunct Colorado Railcar. The benefit of a heavy rail car, constructed of steel, is it can be run alongside freight service.

Although Colorado Railcar was the only manufacturer still making the heavy rail cars, Siemens has indicated it would build heavy rail at its Sacramento plant specifically for SMART.

SMART?s consultant, LTK Engineering Services of Portland, Oregon, is expected to make a recommendation in the spring on heavy versus light rail. SMART is expected to go to bid a year later.

You can reach Staff Writer

Bob Norberg at 521-5206 or bob. norberg