Today's subject is roadblocks.

Not police checkpoints. Not traffic controls for construction work — well, not exactly — but the obstacles preventing more road maintenance, more reconstruction, more expansion on crowded highway corridors.

The primary obstacle, of course, is money.

California needs $72 billion for road maintenance over the next 10 years, according to a survey of cities, counties and transportation interests released last week. Add in bridges, sidewalks and related infrastructure and the figure jumps to $107 billion.

Of that total, about $2.7 billion is needed in Sonoma, Lake and Mendocino counties.

At $25 billion, available resources are less than a quarter of the need.

Gas taxes are the primary source of money for building and fixing roads. The gas tax is a user fee; the more you drive, the more you pay. But with increasingly efficient cars, drivers are using less fuel. Add in rising prices, with a new normal approaching or exceeding $4 a gallon, and people are driving fewer miles, too.

If you're expecting this paragraph to be an argument for higher fuel taxes, guess again. The issue is more complicated.

Yes, motorists ought to pay for the roads they use. But public agencies must spend that money wisely and distribute it equitably. In California, there's evidence of failure on both counts.

Consider high-speed rail. The state is pushing to start construction in the Central Valley this summer, with a goal of eventually linking the Bay Area and Los Angeles, a project expected to cost at least $60 billion. Voters approved $10 billion to get started. But that was in 2008, before the magnitude of the recession was clear. Today, federal funding is in doubt and there's no sign of the private money once promised for this project.

HIgh-speed rail may be in California's future, but it's an extravagance the state can't afford in the present. The first priority should be fixing roads.

If the state paid off the rail bonds early and canceled the project, it would be easier to support a gas tax increase with the revenue earmarked for highways and roads. Work could be expedited by borrowing against future gas tax receipts.

Even then, our second concern remains — inequitable distribution of gas tax revenue.

In the Bay Area, no county has more miles of roads to maintain than Sonoma County. But the formula for distributing gas taxes is weighted toward the number of registered vehicles. On that basis, Sonoma County, with a smaller population, is at a disadvantage.

If that formula isn't changed, and there's little sign of that happening, higher gas taxes could mean that Sonoma County motorists help fix roads somewhere else.

One alternative is to tax drivers based on miles driven rather than gallons purchased, but privacy issues make that politically difficult. Another alternative is extending the local sales tax that voters approved for Highway 101 widening. That would guarantee that the dollars stay in the county, but voters are likely to resist unless they're assured the county has gained control over its payroll and retirement costs.

That roadblock looms large.