[blackeyeblitzar]

> A good two lane street can have similar or better average speed than a bad four lane stroad.

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.

It also doesn't matter that the other two lanes might be repurposed for something else like bike lanes. In my experience, when bike lane projects are forced onto a city by activists, without authentic support from the general public, it ends up just creating a lot of underutilized infrastructure. In many west coast cities it is common to see clogged up car lanes next to permanently empty bike lanes. So even if in theory you could pack those bike lanes with more people (although moving at low speeds), it's never true in practice. The real throughput only gets worse.

[Timon3]

> 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).

[bobthepanda]

the common diet is from four to three (a left turn lane), which is actually better for traffic flow, since left turners now have a dedicated pocket and don't block traffic, fewer people get rear ended, etc.

the problem with how the US does bike planning is that the payoff doesn't happen unless you have a bike network; biking is so unsafe on regular roads that a partial journey on bike lanes doesn't cut it. so often bike lanes get poor usage than they would otherwise get due to lack of connectivity.

[Mawr]

Even if we make the tenuous assumption that the bike lanes are implemented correctly, you cannot expect that people that have lived with car-only infrastructure their whole lives will change their habits overnight. It's going to take some time to reach cycling volumes of even the less developed european cities.