Traffic in Cities: The Downs-Thomson Paradox
Whether you are from California, New York, Austin, or the middle of nowhere Nebraska, we are all too aware of one issue permeating our everyday American lifestyle: traffic. In total, the average American wastes an estimated 54 hours of their life in traffic every single year. That’s more than an entire workweek spent staring at the car in front of you, ironically, most likely on your way to or from the very work you are missing out on. While the simple conclusion we have come to for far too many years is to just build more lanes and more roads for cars to drive on, this effort has been found to be useless, or in some cases even harmful. This is due to a fascinating, ultimately psychological, effect known as the Downs-Thomson paradox.
In simple terms, the Downs-Thomson paradox claims that traffic will increase without limit until the option of public transport (or any other form of transport) becomes faster than the equivalent trip by car. It draws the conclusion that people do not care whether they drive, walk, bike, or take the bus to any location– they just want to get from A to B in the fastest and most convenient way possible.
What is truly remarkable about this paradox is that it explains the seemingly ever-growing car congestion in cities that have poor public transport infrastructure, and shows why cities like Amsterdam, London, and even Paris have noticeably less congestion than most American cities despite having a dramatically higher population density. In congested cities that prioritize cars and ignore public transport, (say busses, for example) a positive feedback loop ensues where people drive cars which slows down the buses, and the increased traffic encourages more people to take their cars!
Thankfully, more and more American cities are learning about this paradox, if not by name, through its evidence. New York has prioritized bus lanes on 14th street in Manhattan, and San Francisco is starting to revitalize its street-car system, realizing the old technology works extremely well with modern safety and efficiency standards.
I find this effect very interesting because it is a real-world example that relates very closely with our discussion on traffic, in which we noted that people will selfishly take their own fastest route, disregarding everyone else. And just like how adding a road of 0 travel time can increase avg traffic, adding more lanes to our road network with no other alternatives simply exacerbates the problem, wasting both our time and taxpayer money. Public transport can provide us a way to decrease the number of people on roads, which decreases travel time and makes everyone spend less time in stop-and-go traffic. While some cities in America are waking up to this phenomenon, it is critical that we continue this change to bring traffic down and reclaim our most valuable asset: time.
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