alt Hacker NewsHaving driven in the UK and coming back to the US I miss all of the roundabouts. Any reason (aside from contractor profits) towns use 4-way traffic light systems vs a roundabout and some yield signs?
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Traffic lights can be tuned to create "green waves" that allows for efficient flow of traffic along arteries through a city. You can adjust the timing throughout the day to help alleviate congestion. In rural areas, heavy machinery/commercial vehicles may need to make a very wide turn through the intersection. Traffic circles are fine for a lot of applications but they aren't strictly better than lights in all circumstances.
Having driven in both, Americans don't take naturally to roundabouts and it would be difficult to teach all the existing drivers about them. Same in the UK when they add new rules: most drivers remain completely unaware of them.
Space/land; you have to displace and buy the four corner properties (at least) to put one in.
Come to Massachusetts, we have a lot of roundabouts and even a few old style two lane rotaries.
A perpendicular intersection uses way less area than a roundabout. That's the basic reason.
Roundabouts have better throughput than a busy 4-way stop, but less throughput than a signaled intersection if the timing and sensing is reasonable (many signaled intersections don't have reasonable sensing). Roundabouts also have some pretty nasty worst case wait times; I'm really not looking forward to the state installing one near me on the approach to a car ferry; it won't be fun to wait for 200 cars to go by before you get a turn to go, and I expect long ferry lines to result in impatient people in the ferry line blocking the roundabout. Sometimes there's two hours between ferry loadings. Going to be some fun times.
Personally, I find it challenging to both look ahead to the right to confirm I have room to enter the roundabout, look to the left to confirm there is no traffic that I need to wait for, as well as looking far left and right to ensure there are no pedestrians crossing soon. Signaled 4-way perpendicular intersections have worse outcomes when a participant doesn't follow the signalling, but indication of right of way makes it easier to confirm at a glance if it's safe to proceed.