Comment by dingaling
1 hour ago
"They work perfectly fine."
The fact that you mention light-controlled roundabouts highlights that they do not, actually, "work perfectly fine".
Roundabouts are a practical example of the tyranny of the majority; minor traffic flows suffer against major. The centre of Salisbury is a perfect example, constantly gridlocked at two roundabouts except at odd hours on a Sunday.
Adding traffic lights to 'fix' this problem then leads to tailbacks on the major routes and congestion on the roundabout, such that the timing sequence for the minor routes are subsequently reduced, returning to the original problem.
Roundabouts, in the plurality, are used as a lazy 'solution' to at-grade traffic crossing, which the road designers themselves presumably don't have to suffer. They also cause pollution from brake dust from slowing and exhaust fumes from accelerating.
> The fact that you mention light-controlled roundabouts highlights that they do not, actually, "work perfectly fine".
I don't think anyone is claiming that roundabouts work in every and all situations: design handbooks often say they're good 'up to X vehicles per hour/day'.[1] But that does not mean they do not work, or not useful, for <X.
Intersections are an engineering problem, and there is a hardly ever an engineering solution that works everywhere and always. There is usually a spectrum of solutions for the various situations that are faced.
[1] https://www.fhwa.dot.gov/publications/research/safety/00067/... § 1.6.1, 3.3.1
Well we have very different experiences driving to, through, and around Salisbury. There's traffic, and it can get bad, but it isn't as bad as you say.
The council and national highways are working on it, but the problem is not one of roundabouts - its one of increases in traffic and lack of capability to make the roads bigger and/or build a bypass. Unless we're willing to knock down a load of housing and cultural sites we're stuck with something around or slightly more than the road capacity we have.