A cogent – and perhaps unanswerable – question punctuates the political machinations over raising billions of new dollars to repair California’s deteriorating highways.

How is it that California motorists are paying some of the nation’s highest fuel taxes, but the highways they use are among the nation’s worst?

Including federal gas taxes, Californians are paying just under 61 cents a gallon, the fourth highest in the nation. That doesn’t include another dime a gallon in “cap-and-trade” carbon fees that, if added, would make California the highest-taxing state.

Meanwhile, data from the Federal Highway Administration place California’s highways as among the worst in physical condition.

Gov. Jerry Brown says the state needs another $59 billion over 10 years for maintenance and repair. He is pushing legislators to act while portraying himself as a “brooding omnipresence” overseeing the work.

But back to the question.

Gasoline and diesel fuel taxes generate about $4.5 billion a year for state and local governments. Overall, the Department of Transportation will spend $10.5 billion during the current year, a third of which comes from fuel taxes and truck weight fees, with most of the rest coming from Washington.

Caltrans is budgeted to spend $1.4 billion on highway maintenance and another $2.3 billion on its “state highway operation and protection program” of roadway improvements that don’t add capacity.

Obviously, spending on those two programs has been too low. Our highway network, once the envy of the world, has been allowed to deteriorate.

Why? There are no definitive answers.

One factor is that the system was largely built during a relatively brief, 30-year period after World War II and four decades later, it’s falling apart just as quickly.

Another is that gallonage taxes have not been adjusted for inflation and fuel consumption has flattened out, thus providing little growth in revenue to match a doubling of pavement-crushing traffic in the last few decades.

Still another is political neglect. While transportation groups have complained for many years about a lack of roadway maintenance, governors and legislators have ignored their pleas – in part because of an ideological conflict over raising taxes that continues to this moment.

Maintenance is not politically sexy. Politicians much prefer cutting ribbons on new projects to appropriating maintenance money, which also explains why many state office buildings and parks are in such sad shape and why many communities are seeing their very old water pipes bursting.

That same attitude extends to Caltrans, where construction engineers and their unions dominate, and maintenance plays second fiddle.

The Legislature’s budget analyst says that Caltrans’ new construction units are overstaffed by 3,000-plus employees – which, of course, their union disputes. But it illustrates the culture – and perhaps siphons off money that should be spent on fixing roads we already have.

If Brown and legislators want motorists to pay even more – the lead Democratic bill would raise the gas tax by a whopping 12 cents a gallon – they should fess up on why maintenance has been neglected. They should also explain how they’ll keep it from happening again.