A beefed-up Caltrain service and a slimmed-down high-speed rail system could run between San Francisco and San Jose by sharing the existing rails, plus just a few miles of new passing tracks, Caltrain officials said Wednesday.

The preliminary findings of Caltrain's long-awaited capacity study, released to a group of San Mateo County city officials, lend support to what is being called a blended system, proposed by a group of Peninsula lawmakers. Containing the high-speed trains largely within the Caltrain right of way and avoiding extensive new construction, the plan has the potential to blunt much of the opposition to high-speed rail on the Peninsula, reduce costs, and modernize the Caltrain system.

"There's a lot of potential benefits here," said Seamus Murphy, government affairs manager for Caltrain. "This gives us a good path forward to work with the (California High-Speed Rail) authority and move forward with this approach."

Lower-impact route

Roelof van Ark, chief executive officer of the rail authority, said that while the results are preliminary, they show that it could be possible to build a lower-cost, lower-impact route up the Peninsula as the first phase of the ultimate system. He said he will meet soon with officials from Caltrain and the Metropolitan Transportation Commission, which is trying to get high-speed rail back on track in the Bay Area. Last month, the authority halted its studies of the San Francisco-San Jose segment, citing uncertainty of what the region wanted.

"This is a good step toward getting high-speed rail going in the Peninsula," he said.

The biggest potential obstacle to sharing the Caltrain tracks has been uncertainty about whether the system has the capacity to support the commuter railroad, which hopes to run more frequent service, and the high-speed rail system, which had plans to run as many as 12 trains an hour.

Preliminary results of the Caltrain analysis, conducted by LTK Engineering, show that the system, with the addition of a four-track segment roughly 8 miles long to allow high-speed trains to pass slower commuter trains making more frequent stops, could handle up to 10 trains per hour. That would allow Caltrain to run six commuter trains per hour during peak times, and accommodate as many as four high-speed rail trains.

The computer model used in the capacity analysis assumed that Caltrain - which would be electrified and use lighter, faster rail cars and an advanced signal system - would run at 79 mph while high-speed trains could travel at speeds up to 110 mph. That would allow every Caltrain, making 13 or 14 stops, to travel between San Francisco and San Jose in an hour or less - times now achieved only by the limited-stop Baby Bullet express trains. High-speed trains would make the trip in 30 to 35 minutes, with one stop in San Bruno.

Early findings

Marian Lee, acting director of the Caltrain modernization program, said consultants will conduct a second run of the model before completing the analysis. The railroad presented its early findings to the San Mateo County Rail Corridor Partnership because of the intense interest, and equally intense criticism of high-speed rail planning on the Peninsula. Lee acknowledged that major elements of the plan are sure to be controversial, including the design and location of the passing track sections, and how to deal with the 50 grade crossings along the Caltrain right of way.

Van Ark said the shared-track plan would still be expensive and require substantial construction. It is still unclear whether it will meet the requirements of Proposition 1A, the state high-speed rail bond, and state environmental laws, he said.