Monday 28 October 2013

Perne Road Roundabout proposal

Cambridgeshire County Council are consulting on safety improvements at Perne Road / Radegund Road roundabout in Cambridge.

The proposals can be viewed here.

Perne Road is also the A1134 Ring Road. All of the Ring Road roundabouts are statistically bad for cyclists' safety and the council want to fix this. That is not in dispute.

The proposals involve moving cyclists onto shared use paths which cross the arms of the four junctions of the roundabout where they would have to give way crossing the arms of the roundabouts.

Just off the plans, the busier north and south arms of Perne Road already have pedestrian signalled crossings about 40 metres away from the centre of the roundabout. The online proposals do not mention upgrading these to Toucan so people on bikes can legally use them.

Cyclists would have to choose using the shared use pavement for safety, or remaining on the road. Shared use is popular with cyclists when uninterrupted, but disliked for the amount of give-ways and hold ups they introduce. Vulnerable pedestrians do not like to share pavements with cyclists, and is a source of constant complaining.

The Dutch have solved many of the issues of two-tier provision, with a three tier provision in busier locations,  clearly separating pedestrians, cyclists and motor vehicles.

One of the arguments against three-tier provision in the UK and Cambridge is that it requires a lot of space, but that is not the case at this roundabout. Below I make a crude comparison of size with a roundabout from Groningen in Holland.

The following pictures are taken from Google Maps at similar zoom levels, rotated for easy comparison.

Google StreetView links:
Perne Road / Radegund Road, Cambridge.
Bakboordswal / Loefzijde, Groningen.

Perne / Radegund Roads, Cambridge

Bakboordswal, Groningen, Holland

Both images combined. Similar sized roundabouts.

I will hold my hands up and say, I do not know if the Dutch roundabout works in practice. I believe the Groningen roundabout is is what cycling campaigners want. It is a subtle change from shared use but has very clear separation. A big question is will the road markings across junction arms work in a UK context on a Ring Road? See the view of a roundabout exit (note driving on right)

My reading of Dutch design is that filtering of traffic is a big part of what they do and cannot be captured from Google Maps.  My gut feeling is that the Dutch route has far less traffic than the Cambridge Ring Road.

The two-tier proposed solution is commonly used in Cambridge and can be safer if you are prepared to stop at side roads and look very carefully but its inconvenient. I find myself unable to use safe facilities for cross city journeys - it just takes too long - and as a result I find myself switching to car or motorbike when I am not in the mood or don't have the legs for fast highly assertive riding required to keep me safe on direct routes.

I'd label shared-use with Safety through Inconvenience. If we could fit in a working Dutch roundabout we could have safety AND convenience. Solutions like this make more journeys viable by bike.

If Cambridge really wants to improve cyclist safety and traffic growth, it needs to be braver with its junction design.

Responses to the Perne Road roundabout proposals have also been made by Cambridge Cyclist and RadWagon.


  1. If there was a 'Like' button on Blogger, as there is on WordPress, I would have pushed it.

  2. A Dutch single lane roundabout can handle 20,000 – 25,000 vehicles per day. Some more information on Dutch types of roundabouts can be read in this blog post: and also here:

    1. According to DfT figures, that stretch of the ring road sees 13000 motor vehicles (13500 PCU) per day, well within the capacity of that roundabout design.

  3. I am sure the Dutch solution is the right one. Even if it is new and people are not used to it I found them extremely intuitive to use in the Netherlands.

    Dual network solutions are just a disaster on so many levels.

  4. I just don't get the idea behind this Perne Road proposal. I keep hearing it's to help kids get to school, but seriously, I wouldn't cycle on the roundabout with my kids as it is, I would walk round, or let them ride on the pavement round (disclaimer my eldest is only 4 so this doesn't seem to annoy people).
    My main worry would be getting them to cross the road, this proposal makes that part no more safe! Who the hell does this benefit? I just don't get it. If I'm cycling on my own no way would I use this facility, I would continue to ride on the road, like I do now.

    If it wasn't being paid for out of "cycling budget" it would make me quite as angry, but seriously, it's so crap!

    The Dutch solution looks great.

  5. Just come across this blog post rather later. I had a discussion with the designer of your new roundabout three years ago. He was determined to build this Dutch roundabout without cycle-paths (I described it to him as being akin to a cheese sandwich without cheese).

    This prompted me to find an example for him of a roundabout with cycling infrastructure connecting to a road without and showing him how all the roundabouts in Assen have cycling infrastructure. i.e. the case that he thought he was copying from the Netherlands basically doesn't exist.

    The safest designs for roundabouts in the Netherlands, and the design which the UK should adopt, does not give cyclists 'priority'. Note that this does not mean they are less convenient. In fact, as a cyclist you have to slow but usually not stop for either type of roundabout. However, there is a huge difference in safety figures here and this will only be more pronounced in the UK where drivers are less used to cyclists. Hence my recommendation of this design.

    Note that the closest Dutch roundabout to the design which has appeared at Perne Road is actually one which we use on Study Tours to demonstrate why this is a bad idea. All of the roundabouts in Groningen are more dangerous than all 21 roundabouts in Assen combined, but this one in particular is especially dangerous. It's that most dangerous design, which has three times the cyclist injury rate of all 21 of Assen's roundabouts combined, which has been emulated in Cambridge.

    You really should be angry about such bad design being copied.