i have always though roundabouts are a good way of keeping the traffic flowing.

That was my understanding but I’m seeing more and more signal controlled roundabouts all over the place. M4 J24 Newport east is now some crazy arrangement with a road through the middle of it as well so that for one route you don’t actually go ’round’. I’m not a traffic engineer but suspect that there’s a level of congestion beyond which roundabouts don’t work – if traffic is coming in a constant stream you can’t join – and as the UK road network gets ever more congested more and more roundabouts ‘break’.

Yeah. I suspect the other issue is that large numbers of drivers completely fail to negotiate roundabouts correctly, so the lights at least keep them at safer speeds.

<sarcasm> Are you suggesting they’re dealing with bad and dangerous driving through expensive changes to infrastructure – I thought that all problems could be solved with a bit of training </sarcasm>

🙂

I thought that all problems could be solved with a bit of training

And helmets. Don’t forget helmets 😀

if that roundabout was built in the UK, there would be “Cyclists Dismount” signs and baffle fences every 10 meters.

The Local Transport Note on cycle facilities says:

The sign to diagram 966 (CYCLISTS DISMOUNT) may be used together with the sign to diagram 965, or on its own. The sign should be provided only where cyclists are required to use a pedestrian crossing facility that they cannot legally cycle on, at the entrance to a pedestrian area, at a location with a low headroom or width restriction (e.g. a subway or bridge) or at places where visibility is restricted to such an extent that cycling would be unsafe

We have fairly decent guidelines in the UK (albeit with a few glaring issues, like merging with main road traffic at narrow points) but traffic planners are free to ignore them.