I'm trying to understand what kind of effect adding lanes has on the effectiveness of highway transport and I...can't. Suppose you have a single lane highway between A and B. In theory, its capacity is infinite.
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In practice, cars can only go as fast as the slowest car on the highway (1). Merging causes slowdowns (2). And accidents stop traffic all together (3). When you add a second lane, you solve 1, you mitigate 2, and you sort of improve 3 (an accident increases merging which slows).
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When you add a third lane, you really get diminishing returns. You slightly improve 2 again, by reducing the chance of merging (from slow roads to fast highways) interfering with another faster car.
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You probably don't improve 3 because there's a 1/3rd chance that the accident happens in the middle of the road, which is very disruptive. And then, even if it happens on the sides, people slow to look at the accident, and emergency vehicles will block other lanes.
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Highways don't have intersections, so it's not like adding lanes increases the capacity of the roads between traffic intersections (avoiding gridlock). According to "credentialed" economists, the reason why adding lanes doesn't work is a concept called induced demand.
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The idea is that by increasing supply (lanes), it will lower the cost of travel (by reducing traffic) thereby increasing demand, negating the new supply. I'm pretty suspicious of this idea, simply because I don't think that adding lanes after the 2nd does much to reduce traffic.pic.twitter.com/o0HthKCLmU
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Additional lanes seem self-defeating. The cars in the far most left lane, to exit, will cross other lanes' traffic, slowing them. Is there something that I'm not understanding here? Or do lanes after the 2nd really give strongly diminishing returns?pic.twitter.com/gz4on8aYL7
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The third and and fourth lanes make a huge difference in throughput in practice. Take a look at I-95 north on a friday afternoon or southbound on a sunday... I don't even want to imagine that shitshow with two lanes only
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You don't need to imagine. Hop on the Merritt - not that bad!
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