Well, we went back to TRL yesterday, to have a go at driving round their Dutch style roundabout.
The actual roundabout itself seemed smaller than it appeared on TV. Each of the approach arms has a different style of segregating the cyclists off the road onto a cycle lane which in all cases is separated from the road by a raised tarmac section (so in that respect it's exactly like the example that we already have in Luton), with different styles of paint and markers for the crossing part. In some cases it's just a zebra crossing, in others a zebra crossing for pedestrians with a different style for cyclists.
We all had multiple journeys to do, testing going in all directions from each arm. The cyclists they were using to go around the roundabout the same time as the cars were TRL staff and contractors (as they said they felt it would be too dangerous to use the public). On each run, they asked us to provide a score out of 10 for both the ease of using the roundabout, and how safe it felt.
On a couple of occasions, I almost ran into the cyclist as they went around.
At the end of the afternoon, we had to fill in a long questionnaire explaining our feelings about each of the options; if we'd noticed the different styles of crossing; and any other comments.
In a test environment, with cars going no more than 10-15 mph and only 1 cyclist at a time crossing in front of you, some of the time, it works fine, but other times it felt very dangerous. With larger vehicles, you'd get roundabouts blocked up and bearing in mind the speeds used in real life, the design just doesn't work. And I told them that. The only way it can possibly work is if speeds are severely limited. I'm not saying that's a bad thing, just I can't see that's achievable here.
Segregation (in this example) doesn't work.