A bit of a follow-up to last week’s post about the Perne Road roundabout, looking at the potential issues, and what could have been done instead.
This roundabout has now hit the headlines because a child has been injured while cycling on the roundabout, on Wednesday evening. I don’t think it’s massively helpful to leap to conclusions on the basis of one incident, but it’s certainly worth looking at the general design flaws with this roundabout, and the alternative ways in which it could have been designed.
For me, the central problem is that cycling has not being designed for explicitly. Instead, it has been bodged into pedestrian-specific design, and into motor vehicle-specific design, simultaneously. Almost all the potential issues flow from this failure. The roundabout design expects people on bikes to behave like pedestrians, or like cars; something genuine Dutch design would never do.
For a start, the ‘shared use’ paths around the edge are quite obviously footways, on which it is permissible to cycle. They are not cycle tracks, with clearly defined routes. The result is cycling in a pedestrian-specific environment, and this, coupled with a lack of clarity, presents a number of problems.
With ‘shared footways’, drivers will have less certainty over where a cyclist might be heading. Take the scenario below, with the path of a cyclist represented by the blue arrow.
The driver doesn’t know if the cyclist is, or isn’t, going to use the crossing. The cyclist is travelling across an expanse of tarmac, and their intentions aren’t clear. The driver may assume wrongly.
Contrast this with a Dutch roundabout (in Assen) -
And the same is true from the perspective of people cycling. They have more time to assess which direction a driver is taking – staying on the roundabout, or leaving it – and therefore will have more opportunities to cross, more safely. Again, this is without cycle priority -
The Cambridge roundabout does not have this cycle-friendly feature. Because the crossing points are not set back any distance from the roundabout, there’s little time in which to assess which way drivers might be heading. In many instances, it may be too ambiguous to take a chance.
Placing the (pedestrian) crossings at these locations close to the roundabout also means they are blocked by drivers queueing to enter the roundabout, rather than left clear, as on a Dutch roundabout, by setting the crossing points back from the perimeter.
Funnily enough, although I’ve criticised the Poynton scheme, this ‘setting back’ of the crossings has been done correctly there, approximately one car length back from the ’roundabouts’.
This means people can cross behind stationary vehicles, rather than trying to cross in front of a vehicle that might be about to jump into the roundabout.
To compound these issues of uncertainty about where people are going, drivers have to contend with people cycling on the road, and on the footway, simultaneously, as they enter and exit the roundabout, rather than dealing with cyclists at one clear crossing point, on defined paths. This is a point John Stevenson makes here -
Drivers don’t know where cyclists are going to be. Because cyclists can either use the main carriageway or the shared-use, off-carriageway paths, drivers are expected to look for cyclists in a number of places at each arm of the roundabout, instead of just one.
Unnecessary complication has been added by putting people cycling on two different forms of route across the roundabout.
Another issue John identifies – having visited the site – is that a shared-use footway, by definition, involves mixing up pedestrians and cyclists together, rather than separating them, and that can be an uncomfortable experience for pedestrians, particularly in areas with high levels of footway cycling. Again, this problem is not one that should have been created.
What effect might the narrowed carriageway have on people who continue to cycle on it? John thinks it might make collisions more likely, as people cycling will be closer to motor vehicles (and there also might be a temptation to squeeze through). That said, the geometry has been tightened, which should lead to lower vehicle speeds – so the collisions would probably on balance be less serious. Swings and roundabouts, although it is obviously far too early to make definitive judgements. In any case, a roundabout with this volume of motor traffic shouldn’t – in principle – be designed with the expectation people will be cycling on the carriageway.
Finally, there has been an awful lot of discussion about whether or not a genuine Dutch-inspired roundabout design would offer cyclists priority over motor traffic, or not. To me, that’s not a particularly pressing issue, compared to the overall design problems set out here. A Dutch roundabout with priority would look very similar to a Dutch roundabout without priority. Cyclists would have clear routes, separated from pedestrians – routes which would make it obvious to drivers what they are doing. Likewise the paths that drivers are taking would be clear, and the roundabout would be designed to maximise crossing opportunity. This roundabout achieves none of those outcomes.
My personal inclination – and I’ve been persuaded on this point – is not to offer cyclists priority, for the main reason that it is safer (remember, this is an entirely new kind of treatment for British drivers), and also because the loss of convenience is marginal, if the roundabout is designed properly. We should remember that no Dutch roundabout offered Dutch cyclists priority, at all, until the 1990s, by law. It was only for reasons of convenience – not safety – that his law was changed, and priority was switched in urban areas.
Priorities can be changed easily – bad design can’t.
Just a quick rough-and-ready size comparison between the Perne Road roundabout, and the Dutch example illustrating this post (which is here, by the way). Not an exact science, but there appears to be more space available at Perne Road.
I think one of the main issues is that the size of the roundabout island itself has been maintained at Perne Road – the island in the Dutch example is considerably smaller, about 15m in diameter, compared to ~23m at Perne Road.
I understand that it would have been expensive to ‘shrink’ the roundabout, due to a culvert, but I think maintaining its size might have led to some of the problems and issues detailed here.