As cost estimates keep spiraling upward and more doubts are raised about the feasibility of California developing a high-speed rail system, several questions keep popping into my head:

If not the present proposal, what could come out of all this? Would developing more extensive regional passenger-rail networks be the answer? After all, in Europe, Japan and China, regional rail networks were extensively developed before high-speed rail was layered on top of them.

It’s hardly surprising, then, that the professionals in the California transportation field are already kicking around scenarios along those same lines.

Stacey Mortensen, executive director of the San Joaquin Regional Rail Commission, is one of those pros. In fact, as head of the organization that operates the Altamont Commuter Express system, she is deep in discussions with transportation officials throughout California about “what’s next?” and “what’s possible?”

“We should look to establishing partnerships among rail systems such as ACE, Caltrain, Amtrak and freight carriers,” she told me. “There are any number of possibilities.”

As Stacey sees it, the San Joaquin Valley still holds the key to establishing a passenger rail system between the Bay Area and Sacramento in the north and the Los Angeles Basin in the south.

Stacey said existing railroad tracks along with dedicated tracks could be used in he valley for diesel-powered express trains running at relatively high speeds.

“If people saw those trains speeding alongside Highway 99, that would really give passenger rail a boost,” she said.

Instead of building the first section of high-speed dedicated rail line between Bakersfield and Chowchilla, as has been proposed, build it between Bakersfield and Palmdale through the Tehachapi Pass, Stacey suggested. That would make rail service from the San Joaquin Valley to Los Angeles a reality. At present, Amtrak passengers take a bus between Bakersfield and L.A.

In the Bay Area, regional trains could use ACE, U.P., BNSF, Caltrain and Amtrak tracks.

High-speed sections that would be elements of these cooperative ventures could someday serve as starting points for development of an integrated high-speed system.

And what would all this mean for passenger-rail service through Tracy?

Tracy Mayor Brent Ives, a longtime member of the San Joaquin Regional Rail Commission’s board, said there is still a possibility of establishing a dedicated line for passenger rail over the Altamont Pass.

The dedicated tracks, including tunnels, through the Altamont Hills are a central element of the proposed Altamont Corridor Rail Project, a part of the statewide high-speed rail proposal that envisions semi-high-speed trains connecting to main high-speed lines. A dedicated Altamont line would eliminate conflicts with U.P. freight operations and allow increased speeds for passenger trains, which could connect with BART at or near Livermore.

“Even before the high-speed rail project came along, we had established a need for a dedicated line connecting the San Joaquin Valley to the Bay Area,” Brent said.

Although cost estimates vary, he said acquiring right-of-way, delving tunnels and building the tracks in the Altamont might not cost more than $500 million. That is a lot of money, but when compared with the figures being tossed around for the full-blown high-speed system — $100 billion and counting — it sounds a lot more reasonable and financially feasible.

Federal transportation funds could perhaps be combined with high-speed rail funds for such a project, Brent said.

“ACE has a good reputation in Washington, D.C.,” he noted. “It’s up and running and a success.”

And if the ACE route through Tracy could use some existing tracks as well as dedicated ones, it might not need all the proposed elevated structures that would change the landscape around here considerably.

If that Altamont line could somehow be established — the stretch between Tracy and Livermore is already being considered as a possible first phase — it just might become part of a north-south passenger-rail network, especially if the proposed high-speed route through the Pacheco Pass is put on hold.

It wouldn’t be the first time rail passengers had passed through our town en route between the Bay Area and L.A.

The San Joaquin Daylight for many years went through here each day, and The Owl in the evening.

Obviously, everything involving passenger rail — high-speed or not — is in flux, and there is a great deal of conjecture involved in all these scenarios. But under the present financial conditions, some elements of present discussions could emerge that would have a much better chance of seeing the light of day than the currently proposed high-speed rail system in California.

• Sam Matthews, Tracy Press publisher emeritus, can be reached at 830-4234 or by email at shm@tracypress.com.