You are right that they require a slightly bigger footprint.
https://www.acsengineers.com.au/2016/08/22/roundabouts-vs-tr...
The biggest roundabout I’ve personally driven was an intersection of 2 freeways and a major city throughfare. 5 lanes in the circle itself, all at speeds up to 90kph.
They’ve since added stoplights on it because people were being dumb and blowing through the whole thing at ridiculous speeds.
It's rare that I stop at a junction that requires me to cross a traffic flow, lights or no lights, that I don't wish that a roundabout had been put there instead.
Collisions can at times bring a roundabout to a halt, but more often than not, people just use common sense and move around any obstacle, while maintaining as much lain discipline as they can.
Cyclists, so long as they behave as if they are cars, also rarely have issues at roundabouts. I'm quite accustomed, in my area, to following a cyclist around a roundabout, paying attention to their hand signals, and giving them plenty of space.
Basically, it comes down to training and practice. In the UK, if you can't handle a variety of roundabouts, you'll fail your driving test.
As a cyclist, sometimes in roundabouts, this is something that many drivers need to be more aware of. In particular, depending on the roundabout size, the entry angle, and the car, someone's A pillar may completely obscure a cyclist.
Also, while a great solution for cars, in populated areas, roundabouts can be tricky for pedestrians to cross. Also not aided by the fact that at least in Germany many motorists have no clue about the exact rules (yield to crossing pedestrians and cyclists when exiting the roundabout because that's effectively a turn). The best solution in this regard still seems to be to put zebra crossings all around the roundabout, along with traffic islands between the lanes entering and existing the roundabout. That makes it sufficiently safe for people and bikes to cross and sufficiently obvious to drivers how to behave. But that takes even more space.
In fact, there are two roundabouts in Worsley/Walkden. Though those cause a huge amount of traffic in rush hour.
Pretty much any journey I take in the UK involves at least one and could be upwards of 10 to 20 for longer distance drives.
The thing is until people are used to them - which can take years if not decades - they can be slower. And they can be hard to retrofit into older locations. In cities it may be better to turn streets to one way (making all turns “right turns” effectively).
Edit: 7 lanes in this particular one: https://goo.gl/maps/HpFvtHeFTC5om81NA :o
So devise an automated devil’s traffic circle with cars going in all directions.
If it's the urban core busy city center where there are skyscrapers right up to the lot line, there's no room for a roundabout unless you're willing to make 'round a bumps' or carve some footprint out of the buildings at traffic level.
If it's the busy city center where you've got four lane surface streets intersecting with each direction having two straight through lanes, one right turn lane and one or two left turn lanes, a roundabout is never going to manage that kind of throughput by forcing all those people into a single lane to get into the roundabout at low speeds.
You may have fewer collisions, and of course very few of them will be during left turns, but you'll also reduce the utility of the roads connected to the roundabout, which will likely move traffic to other roads. Also, a collision in the roundabout stops the roundabout, which makes it hard to respond if people are injured or vehiclea disabled.
Traffic signals with 'protected' lefts don't stop people from going against the signal, but they do stop a lot of people from trying to make a gap that they really shouldn't. Sometimes a three-way signal timing pattern is appropriate; for the main direction, opposing traffic has greens for straight simultaneous (with cycles for protected left if appropriate), and for the other direction, each side gets a green for straight and left one side at a time.