I'm sure, like many of your readers, I've not been able to understand how County Highways can claim the NDR roundabouts are designed correctly and yet driving round them they seem quite dangerous.

Particularly the use of concentric lanes tends to encourage cars to stay in the inside lane to go straight across when other traffic will assume they're turning left. This seems to be backed up by dashcam footage and anecdotal reports.

Having checked the government's guidance on the matter, I found this important paragraph about using concentric lanes on roundabouts:

'4.12 Concentric markings which divide the carriageway into more than two lanes have limited use on wide circulatory carriageways since they have been found to encourage the 'tramline' effect. In this case, a driver may remain in a particular lane until reaching the desired exit, and then deviate across other circulating movements in order to leave the roundabout.

This behaviour can increase the potential for side-to-side vehicular conflict on the circulatory carriageway.'

Yes – that's what's happening on the NDR, and it's a well understood consequence of this type of marking. Sorry Norfolk County Council – your highways teams have just got this wrong and it needs fixing.