Arizona Rail Passenger Association

by William Lindley October 31, 2000A recent topic of conversation on the All-Aboard mailing list was the question: Do passenger trains (whether urban, regional or intercity) reduce auto congestion?

David Pedersen wrote:

“It pains me to see fellow rail advocates state that trains will reduce auto congestion. There is no way any train anywhere will reduce congestion. The need for transportation is growing so fast that any cars/trucks taken off the roads are replaced with 2-3 more. Additional air service or more roads does not reduce auto congestion either.”

“The Dane” writes:

“I’m sorry to disagree with you on this point but I must. Trains everywhere reduce highway congestion. The roads between Washington D.C. & New York City would be swamped if train service was to cease. New York City would grind to a virtual standstill if the Subway were to stop running.”

It sounds like a paradox but they are both correct!

While removing trains may dramatically increase road congestion, the converse is not necessarily true. I suggest that:

When you remove train service,

congestion increases; yet

When you add train service,

there is a negligible effect on congestion but a large positive social and economic impact.

Why?

In the widespread case of a city whose highways are plugged with far too many cars, people use surface streets, delay their trips, or simply do not travel. The last part — people not traveling — is positively frightening because it has a huge negative social impact (people stay home) and a huge negative economic impact (people who stay home don’t spend their money).

What happens if you introduce a rail system to such a city? Some people who formerly drove will ride the train.

Imagine the space occupied by one commuter’s car suddenly being empty on that congested highway. What happens? The driver behind him moves up. The back-up is twenty feet shorter, the congestion delay one second less.

However, the way people perceive congestion is at the bottlenecks. And by definition there is always more traffic trying to enter a bottleneck than it can handle. Thus, even though we have removed that commuter’s car from the road, there is no appreciable effect on congestion.

Furthermore, any congestion reduction causes those people who formerly stayed at home to consider traveling, and the folks who delayed their trip will be more likely to travel at the more convenient peak times.

However, once your train service is well-used, suddenly removing it puts all the former rail users on the road at those same peak times. That is the paradox.

The better argument for rail service then is that adding trains (buses, bicycles, and any other alternative) has a hugely positive social and economic impact. Happier people, a higher “velocity of money,” better employment, and so on.

– William Lindley

Arizona Daily Star, 30 October 2000.