What happens when you go through years of planning and actually building TODs, only to have the T suddenly vanish?

This is the question on the San Francisco Peninsula and in the South Bay, where Caltrain is proposing radical service reductions and the closure of numerous stations.

It's also a question that other places are likely to confront as public budgets grow more austere and the Republican Party ramps up its attacks on seemingly all transportation that doesn't involve automobiles.

Caltrain is the heavy rail commuter service that runs from Gilroy to San Francisco. It carries nearly 40,000 passengers a day on weekdays. The Santa Clara Valley Transportation Authority, the San Mateo County Transit District and San Francisco jointly operate the system. However, Caltrain has no dedicated funding source, such as a local sales tax, and the three Caltrain partners have their own serious money problems. Thus, Caltrain faces a $30 million budget deficit for the 2011-12 fiscal year.

To close the budget gap, the Caltrain joint powers board has proposed reducing the number of weekday trains from 86 to 48, eliminating all non peak-hour trains, eliminating all weekend and special event service, ending service between San Jose and Gilroy, and closing seven stations from South San Francisco to San Jose.

The proposal is a blow to the cities and the region as a whole, which have embraced transit-oriented development (TOD) adjacent to Caltrain stations. Projects have been built in South San Francisco, Redwood City, Mountain View, San Jose and elsewhere. A wide variety of TOD projects is planned in Millbrae, San Mateo, San Carlos, Sunnyvale and other locations. Cities have created mixed-use land plans around Caltrain stations. Moreover, Caltrain is critical to the Grand Boulevard Initiative, a voluntary regional planning effort that seeks to transform the El Camino Real corridor – which includes many miles of the Caltrain line – from a mostly automobile-dominated, inefficient, commercial strip into a dense, mixed-use, transit-first corridor.

The Grand Boulevard Initiative and Caltrain are not dependent on one another, observed Michael Garvey, the primary consultant to the initiative. Still, he said, "A lot of our planning is based on the assumption that the major transportation utilities would be in place."

You'd think that, with regard to Caltrain, the assumption would be safe. After all, trains have carried passengers along most of the route since the late 19th century.

The whole point of the Grand Boulevard Initiative is to locate many new job centers and housing units along a corridor that already has a great deal of infrastructure, including public transit in the form of buses, light rail and, yes, Caltrain. Even cities that for decades have been hostile to growth have shown a willingness to accommodate transit-oriented development along El Camino, thanks in large part to the popularity of Caltrain. All of this is exactly what SB 375 seeks to encourage. It's what the new urbanists, smart growthers, housing advocates and the alternative transit crowd have been pushing for.

But if Caltrain's budget-cutting proposal goes forward, are any of these plans and good intentions viable?

Elected officials and advocates are trying to find funding for Caltrain. I have to believe they will be successful, later if not sooner. Still, the episode is making both decision makers and transit riders nervous, and it has to raise big doubts. How committed will cities and developers – not to mention merchants, business owners and potential residents – be to transit-oriented developments if the transit can vanish? Roads and highways may become heavily congested, but they don't disappear.

– Paul Shigley