If Yogi Berra were to comment on the MBTA, he might put it this way: It's so crowded, no one uses it anymore.

Commuters on the Green Line stand the entire 45-minute trip in and out of the city. Riders disembark from a sweltering train at Alewife only to find themselves stuck in line for a half hour as they wait to exit the parking garage. Red Sox fans pouring into Kenmore Square are nearly crushed.

There is one exception to this misery. The Purple Line commuter rail trains - particularly the double-decker trains - are fast, comfortable and civilized. Lucky commuters at North and South stations love them. That, of course, only underscores the flaws of the rest of the system: Everyone else, it seems, is second class.

The MBTA is now operating at close to capacity. But at the times when people need it, particularly rush hour or for special events, the system is overwhelmed.

And those who travel by car? Sure, they may be stuck in traffic. But at least they're sitting, not standing. Their air conditioning is on, hot coffee is in the holder and nobody's armpit is in their faces.

None of these, of course, are new complaints. Riders have been grumping about the T for a long time with no effect. Local pols blame the state. State pols blame the MBTA. And the MBTA, a quasi-independent agency, is elected by no one. It's a brilliant strategy for escaping responsibility.

Perhaps this wouldn't matter much if all you had were unhappy commuters. But, particularly for urban areas like Cambridge and Boston, the failures of the region's public transportation system are cramping economic growth.

Planners working for agencies such as the Boston Redevelopment Authority will tell you that transportation issues, particularly parking and traffic problems, are the single biggest constraint on developments. Residents, particularly those in Cambridge and Boston, resist the surge of cars that each new project brings. They don't believe officials who swear that everyone will use the T because they know it's overloaded. They don't believe politicians who claim this time will be different because last time, when they got the same promise, it turned out it wasn't different after all.

Consider, for example, plans to build a new Fenway Park.

The Red Sox want to increase the size of their ballpark by 10,000. The most legitimate source of community opposition comes from residents who fear, rightly, that fans arriving by car will turn the already overtaxed streets of the neighborhood into little more than gridlock.

Oh no, comes the rejoinder. They'll all use public transportation.

We'll upgrade the Fenway Park stop. We'll use shuttle buses. When we're done, it'll be even better than before.

Except, of course, that a critical piece of the new ballpark's plan is the construction of two new parking garages. The garages are expected to be profitable, so profitable, in fact, that they will subsidize other improvements and perhaps help the Sox pay for a portion of their own costs.

So how sincere, really, are planners who they say they want fans to use public transportation? After all, if they were successful in doing so, then the financing for the entire project would fall apart.

Contradictions such as this are easy to find. Proposals to improve pedestrian access on city streets are denied state grants because the program only gives money for projects that enhance traffic flow. Boston cleverly keeps parking fines low because high fines would discourage people from parking illegally and would cost the city a valuable source of revenue. A sensible idea to connect North and South stations while construction for the Big Dig in under way is ignored. Indeed, the long promised Silver Line, which was to have been a light rail system connecting Roxbury to downtown Boston, has turned out to be just a fancy name for a bunch of new buses.

The striking thing about public transportation in Boston is that while it is quick to get praise, it is very slow to get money. What the MBTA plainly needs is a few billion dollars to expand its capacity. Other cities around the country have been pouring money into their systems.

Within the last few weeks, for example, Los Angeles has opened miles of new subway tracks. Not in Boston, of course, where the Big Dig - a project for cars, not public transportation - is sucking up every available dollar.

It's a sad state of affairs. And it explains why, as grim-faced T riders watch out their windows at the passing cars, there is usually only one thing on their minds.

Envy.

Tom Keane writes every Friday in the Boston Herald. He can be reached at tomkeane@tomkeane.com.