[drdavid]

My company modeled traffic before I sold it.

Roundabouts (or 'rotaries', depending on where you live) and yield signs could do a whole lot to reduce travel times and increase efficiency by a surprisingly large amount.

The problems are numerous, but mostly the urban areas weren't designed for such, the costs to switch would be large, and the American driver can take up to six years to adjust to a new traffic pattern.

[Mountain_Skies]

My rural county has gone wild for roundabouts. It appears we got a new traffic engineer about five years ago and they've set about to make as many roundabouts as possible. We even have a double roundabout now. I'm surprised by how little controversy it created and how quickly everyone adapted. I can only think of one that hasn't worked out well and that's because traffic from a very close Chick-fil-a ends up back up into the roundabout and clogging it up.

Due to the rural/exurban character of the area, space for roundabouts isn't much of an issue. I suspect lots of other similar counties could do the same with similar results but it takes someone in the planning office to take the chance on doing it. Also it takes money so from a fiscal point of view, it's best to redo intersections when they're already scheduled for being repaved or they're having capacity issues that need to be addressed.

[sandworm101]

My rural area has rules against roundabouts. Depending on dimensions, they can be difficult for large farm machinery to negotiate. And in in the winter they are more difficult to plow.

[kwhitefoot]

That's strange. We have lots of roundabouts here in Norway and the farmers don't have any problems, nor the snow ploughs.

Perhaps ours are a different design?

[bradstewart]

For reasons that are unclear, a lot of roundabouts in the U.S. are so small that its nearly impossible for two vehicles to be in the roundabout at the same time.

Which makes them basically useless, and difficult navigate for e.g. vehicles with trailers--you end up running dragging the trailer over the center or something.

[kwhitefoot]

Small roundabouts in Europe are typically just a disk of white paint in the middle. Anything too big to go around just drives over it.

[actually_a_dog]

There are a lot of these in Berkeley. On top of being small, they have stop signs at the entrances, too! I tend to believe they're mostly an excuse to put a tree in the middle of the road, because a lot of them do have trees in the center.

[drdavid]

That's actually measurable. You take the data from before the change and the estimations (based on similar changes elsewhere) and plot how long it takes for the traffic to reach expectations (in terms of things like throughput and decreased collisions). With that, you can find out how long the average drivers took to adjust.

It can be depressingly long.

[fomine3]

Roundabouts everywhere is what I built on a city in Cities: Skylines. I wish there are more roundabouts in real world.

[actually_a_dog]

OTOH, roundabouts with stop signs are just the worst of both worlds. I've seen this distressingly often. Looking at you, Berkeley....