Does Public Transportation Save Energy?

No.

Public transportation, like any other activity, uses energy. But the implication of the question is that public transportation uses less energy than the alternative of no public transportation.

But this is also false.

Let's make optimistic assumptions about public transportation; i.e., assume that it's widely used -- and buses are packed with people around the clock. For that matter, let's also assume that every one of these people would have otherwise used the most gas-guzzling vehicles they could find.

Those public-transportation people therefore use less energy than if they drove instead. And that implies that the supply of energy sources (like, say, oil), would not be depleted as quickly. And that would keep oil prices low; i.e., more oil = low oil prices.

So far, so good: Public transportation looks like a "winner".

But...those low oil prices would induce motorists to use more energy, leaving us back where we started, energy-wise. And if the government artificially keeps oil prices high with lots of taxes to "conserve" oil, then oil will become more abundant elsewhere in the world, like, say, China. The oil will still be used, but not by us.

Also, an unintended (?) result of subsidized public transportation is that it artificially raises the demand for all travel -- and that in itself increases the total amount of energy used by all transportation. For that matter, transit "advocates" constantly claim that highway congestion cannot be solved by constructing new highways because the new highways will fill up almost immediately. Well, if that's the case, then why wouldn't the empty highways resulting from nearby public transportation construction also fill up almost immediately?

Why should it be a government policy to encourage people to use transportation more than they would without taxpayer-supported "incentives"? If the goal is to use less energy, then shouldn't the government be discouraging transportation? And yet, public-transportation users are not expected to pay their way. (And, in all fairness, neither do motorists -- there are hardly any road-user prices anywhere.)

So, it looks like public transportation has no effect on the total amount of energy used, increases the amount of energy that transportation requires, and presents a large bill to taxpayers.

None of this is to imply that public transportation (or, more accurately, mass transportation) is intrinsically bad, but the claim that it saves energy is false.