“What were they thinking?”

That’s the cliché question everyone asks when wondering how someone thought up some cockamamie idea.

Remember several years ago when Coke decided it needed a new taste? Or when General Motors’ president Roger Smith let film maker Michael Moore expose the GM head’s lack of imagination, intelligence and know-how in the revenge comedy film classic “Roger and Me”? Or when President Clinton did you-know-what with you-know-who in the you-know-where?

Now it is the MBTA’s turn to play idiot. How could they come up with such a hare-brained scheme (sorry, hares) as to pour 60-foot buses every four minutes into downtown Boston between Beacon Hill and the Boston Common when they have a perfectly good streetcar line, the Arborway line, that gets from the same place — Forest Hills — to the same place — Park Street Station?

Couldn’t they figure out that every vehicle on the streets of downtown Boston contributes to traffic jams, frustrations, noise and, no matter how “clean” the fuel, pollution?

Couldn’t they figure out that they already have a right of way that, like all Green Line rights of way, allows streetcars to move faster than the vehicles on the streets adjacent to it?

Couldn’t they figure out that riders prefer a tried and true streetcar to a lurching bus that sputters along with the traffic, rather than cruising along on its own turf?

Couldn’t they figure out ahead of time that the neighborhoods through which they propose to extend this bus line — Back Bay and Beacon Hill — would say, “Not a chance, Buster.”

Couldn’t they figure out that streetcars have some appeal to communities and that buses are what communities believe they get when they have no power?

When the T eliminated the Arborway streetcar in 1985, they were obligated to put it back or to come up with an acceptable substitute. Jamaica Plain wants its streetcars back. The T is trying to get away with buses, which they say are good enough.

The plan T officials recently presented to neighbors in Jamaica Plain is so hilarious that we have trouble reading it with a straight face. These officials claimed they preferred buses because buses could more easily get out of an ambulance’s way. That would be true if the streetcars used the street. But the last we heard, streetcars didn’t have to get out of the way of ambulances since streetcars rolled along over their own rights of way. They would conflict with ambulances only at intersections, a small percentage of the route.

If we drove ambulances, we’d be thankful we didn’t have to negotiate 60-foot monoliths blocking our way every four minutes at rush hour. We’d like to know where these monoliths will be able to go to get out of the way in the traffic that clogs Huntington Avenue, Boylston Street, South Charles Street and Beacon Street.

The reason the MBTA is floating this proposal is probably money. Like many long-time governmental (and private) bureaucracies, there is a lot of dead weight at the T that taxpayer funds are supporting. At the same time, there is a false notion here in the land that we taxpayers don’t want to pay for good services.

Squelch that thought. From what we hear from neighbors on Beacon Hill — and we’re the ones who pay the most — we’d actually like to pay for some good services.

Those who like to drive their BMWs at top speed would prefer to travel through the city unencumbered by 60-foot buses. Those who live along Beacon Street would like to listen to moving traffic, not frustrated drivers honking in traffic jams. Those who ride in from JP have said unequivocally they’d prefer the streetcar to the bus.

We didn’t get calls back on this matter from the MBTA’s press office. Do they know this proposal is indefensible?

On the one hand, we love proposals like this. It makes great front page news, as it was last week in The Beacon Hill Times.

On the other hand it makes us profoundly sad. The T has some responsible, devoted public officials. The Red Line is Beacon Hill’s savior, as is the Green Line for the Back Bay. As noisy and as ill-kempt as it is, it can get us to Harvard Square faster than an automobile — remember more than 30 years ago when the T boasted on signs that it was eight minutes from Harvard Square to Park Street?

The T can do better for all of us than this sorry proposal. Give Jamaica Plain their Green Line streetcar back. Keep our downtown street free from 60-foot buses.