Roundabouts can run into efficiency issues when the two traffic directions don’t have roughly even flow. The shortcut roundabout seems as though it is intended for intersections with a primary and secondary route, with the primary route having the through lane
Note that your proposed roundabout will not be as safe as a traditional roundabout as the through traffic and circulating traffic can collide at a right angle and at a decent speed (the deflection in the middle isn’t going to be super effective at slowing vehicles, but I love that you thought to include it!). The safety benefit of a roundabout comes from reduced speeds (due to pre-deflection and circulating speed) and the reduced impact angles, both of which are affected by your proposal.
Drivers doing a u-turn while vehicles are stopped on the circulating carriageway at a first pass makes me very uncomfortable but I’d have to think about it seriously / do research on it to work out whether it’s actually a bad idea or if I’m just afraid of anything different to the status quo. Early thoughts are it will confuse drivers (both not knowing how to perform the manouvre/that they can perform the manouvre, and also drivers who witness vehicles doing it won’t be sure what’s happening), and the efficiency benefits are probably minor
Note that my specialty is in improving safety rather than efficiency. I have experience in project work where I had to balance them, but the above is all strongly biased towards discussing safety.
From a traffic engineer’s perspective:
Roundabouts can run into efficiency issues when the two traffic directions don’t have roughly even flow. The shortcut roundabout seems as though it is intended for intersections with a primary and secondary route, with the primary route having the through lane
This sort of “hamburger” roundabout is similar to your proposal: https://www.bristolworld.com/news/hamburger-roundabout-plans-for-a4174-bristol-ring-road-shelved-after-overwhelmingopposition-3443196
Note that your proposed roundabout will not be as safe as a traditional roundabout as the through traffic and circulating traffic can collide at a right angle and at a decent speed (the deflection in the middle isn’t going to be super effective at slowing vehicles, but I love that you thought to include it!). The safety benefit of a roundabout comes from reduced speeds (due to pre-deflection and circulating speed) and the reduced impact angles, both of which are affected by your proposal.
Drivers doing a u-turn while vehicles are stopped on the circulating carriageway at a first pass makes me very uncomfortable but I’d have to think about it seriously / do research on it to work out whether it’s actually a bad idea or if I’m just afraid of anything different to the status quo. Early thoughts are it will confuse drivers (both not knowing how to perform the manouvre/that they can perform the manouvre, and also drivers who witness vehicles doing it won’t be sure what’s happening), and the efficiency benefits are probably minor
Note that my specialty is in improving safety rather than efficiency. I have experience in project work where I had to balance them, but the above is all strongly biased towards discussing safety.
Right.
That’s another name for the “through roundabouts” I mentioned.
On the other hand, there are no points where traffic has to cross/merge 2 lanes at once, like in a turbo roundabout.