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> Can you provide a more specific argument or evidence? To me, it seems obvious that two lanes has less capacity than four lanes. Therefore, a two lane road will have worse traffic, all other things held equal. While it's true that two lanes have less capacity than four, it's also measuring the wrong value - throughput is what you want to optimize for. This means you have to take a bunch of additional factors into account, for example: - How many lanes do the connections to other roads have? Any time you're reducing the number of lanes, you're creating potential bottlenecks. If you have one lane, then widen up to four, and narrow back to one, you'll most likely have worse throughput than if you'd just kept one lane. - How much space do you have for switching lanes? The more lanes, the more time people need to get into the correct one for their destination. You need to telegraph exits etc. much earlier. - Do surrounding roads have space for the additional induced traffic? Time and time again, extra lanes have made traffic problems worse instead of better. There are of course also disadvantages, e.g. the impact of any single lane being blocked. It's a complex and fascinating topic, especially considering the similarity to other networks (e.g. computer, biological). |