Roundabouts in the US

I think it'd take a traffic engineer to answer that question anyway, and it'd probably depend on the volume and direction of traffic. The only roundabout like that around here has traffic compressing considerably before the roundabout so...I don't know.

...and would probably involve things such as cost, location, traffic flows etc...

Anyhow, the British Road Design Manual is in a 15-volume guide — perfect bedtime reading...

edited 2nd Jul '11 11:17:00 PM by Greenmantle

Presumably the lane on the roundabout would be as wide as the three lanes leading up to it; rather than merge traffic into a narrow lane the lane is wide enough to accomodate traffic. That way on approach if you're going right, you stay right, if you're going straight on you stay in the middle and if your going left you stay left.

Maybe a multi-level roundabout? Have the left lanes feed in/out of the ground level, the right lanes to an elevated circle?

so it would go up then down then around and oh god I've gone crosseyed.

A multi-level roundabout?! That's preposterous. But not a bad idea.

Don't they already exist?

Try J10 M6 and any of the Birmingham Circuses — and damn it, any Roundabout Junction — they're not exactly hard to find here...

edited 3rd Jul '11 2:16:28 PM by Greenmantle

That's a raised roundabout. That's as common as hell. I think he was talking about layered roundabouts, as in, stacked.

Raised anything is double the price, and before you ask, underground anything is triple or more.

Maybe I'll revive this thread next year after I take a related class. Transportation Engineering, I think it's called.

They exist too, no doubt.

@ Mad #84: Try driving in the San Fransisco Bay Area before? On the east side of the bay, I think it's Telegraph Avenue that goes through at least six different townships - so you have 100 Telegraph Avenue, Oakland. Then four blocks down, 100 Telegraph Avenue, Berkeley. Another half a mile is 100 Telegraph Avenue, Walnut Grove. I can only imagine how much worse it would be if the street name changed when you switched which local authority owned it.

The only modern city I've driven in that isn't completely screwy is Las Vegas, and even it has some doozies (the Spaghetti Bowl interchange, Boulder Highway).

All the roundabouts I've seen have been in the Washington area, and a few while I was in Cape Cod a few years ago, and every one of them has been a goddamn nightmare for traffic and pedestrians alike. The main reason they don't get crashes more often than they do is because people do their damndest to avoid them altogether.

edited 11th Jul '11 12:46:17 AM by Pykrete

^^ Ninja: No, but I grew up close enough to Chicago to know what happens when a city absorbs its suburbs, and the town I actually lived in was one of four that formed an unbroken chain up the Fox River, so there were two long thoroughfares (one on either side of the river) that changed names at least three times as they passed through each one.

And the town I live in now is the westmost of three that have grown together — and each one uses a different street-naming system: in mine, it's numbered <Street>s run perpendicular to the river, numbered <Avenue>s run parallel to it; the next town east it's the reverse - numbered <Avenue>s are perpendicular, numbered <Street>s are parallel; then in the next one east it's back to the same way as in mine. So when you cross the city line on 18th, you go from being on 18th Avenue, to being on 18th Street, then back to being on 18th Avenue.

edited 11th Jul '11 7:56:13 AM by Madrugada