Comment by max76
6 years ago
I'm unsure about the Detriot specific case (it might have an unusual number of road crossings on very high traffic streets) but I'd suspect it would reduce congestion by taking cars off the road. Most commuter trains have this effect.
They're not necessarily taking cars off the SAME roads though (think arterial highways vs surface streets).
There's also Braess' Paradox to be aware of, which means that reducing congestion can actually INCREASE congestion. https://brilliant.org/wiki/braess-paradox/
I think you misunderstand Brasess' Paradox. It is when adding to a system decreases the efficiency of the system by adjusting the Nash equilibrium to be further from the optimal system wide solution. "Reducing congestion increases congestion" is a not a logical statement.
My comment left the possibility of Brasess' Paradox open in the specific Detroit case, but practically speaking commuter trains are used by most major cities worldwide as part of a comprehensive transportation system. For many cities rail is among the most efficient subsystems of their transportation system.