Monday, 10 September 2012

The fatal/serious bike casualty rate per km in London is 30x that for cars; And why bikes need more space because they take up so little

TfL have published a study (under 'Research reports' here) entitled 'Levels of collision risk in Greater London' that I think only gets really interesting on the very last page. Table 4.10 on that last page includes what I think are the first TfL calculations of casualty rates per kilometre travelled in London for different modes of transport. By combining the number of casualties in 2010, estimates of total distance travelled by each mode and assumptions on the average occupancy of each mode, they come up with the following figures for the rate of fatal or serious casualties per 100 million 'passenger kilometres'.

In case you can't read the numbers, they are 73.9 for bikes, 84 for motorcyclists, 2.5 for cars and taxis, 1.0 for buses and 0.4 for goods vehicles. So some good news for our put-upon HGV drivers there. The other interesting thing (okay, maybe only to me) in that table are the TfL estimates for average occupancy of different modes. They say the average car has 1.2 occupants, the average bus 16.6, the average bike just 1 (what, no backies?). Bear in mind that TfL already assume (table 1 on p. 67 of this PDF) that on average a bike takes up just 20% of the road space that a car does (in technical terms it has a 'PCU' or Passenger Car Unit of 0.2), a bus takes up twice as much, and so on. Put these two sets of numbers together and you get a figure for 'Persons per PCU', which is basically a measure of how efficiently each mode of transport uses road space.

Persons per vehicle PCU per vehicle Persons per PCU
Cyclist 1 0.2 5
Motorbike 1 0.4 2.5
Car/taxi 1.2 1 1.2
Bus/coach 16.6 2 8.3
Goods vehicle 1.3 1.65 0.8

Going by these figures, buses use the road space most efficiently (NB none of this includes energy efficiency) and cars the least efficiently (goods vehicles are there to carry goods not people so this measure has fairly limited application to them). Referring back to the figures on casualty rates, we can conclude that buses are both very safe and very space-efficient, which is great, while bicycles are very space-efficient but (relatively speaking) much less safe, which is bad. Obviously cycling could be a lot safer if London had cycling facilities like they do in Amsterdam, Copenhagen, Berlin, Stockholm and various other European cities. The high space-efficiency of cycling is, I think, just another reason that TfL should be copying what those cities have done - that is, giving bikes more space in part because they take up so little.


  1. Hi Jim, there's an interesting little chart on the first page of the Introduction to Cycling: the way ahead which slightly contradicts your claim that, compared to other forms of transport, buses use the road space most efficiently. I understand that your maths is correct, but maybe the bus does well in London because the bus network is considerably better developed than the cycle network, and/or more space is given over to the bus. According to research carried out by Botma & Papendrech, when all things are equal the number of people crossing a 3.5 metre-wide space in an urban environment during a one-hour period is 2,000 for the car, 9,000 for the bus, 14,000 for the bike and 19,000 for the pedestrian. 

    Under Ken Livingstone, I think it is fair to say, London experienced a bus revolution. Boris Johnson is promising a bicycle revolution. It will be interesting to see, therefore, what happens to CS5. As a rule of thumb, through Peckham and Camberwell the road is three lanes wide. Currently, two lanes are given over to private motor traffic, and one to bus traffic (sometimes the bus lane is on one side of the road, and at other times on the other side). We know that the Vauxhall Cross junction is due to be given the Go Dutch treatment, but just sorting out a junction here or there is not really very much help if the bits in between still feel dangerous. So what will happen? This is a Cycle Superhighway, remember. Like I say, it's going to be interesting. I would be surprised if the space was taken from the private motor vehicles - they have to be able to go back and forth, after all, and there's hardly any on-street parking - which basically means that if the bicycle is to have its own segregated space, it's got to be reallocated from the pedestrian, the bus, or both. Nice and squeezy?

  2. Thanks for the link and the interesting comment, Simon. I guess the bus/bike comparison depends heavily on the average number of people per bus. Perhaps London buses tend to be more crowded than those in Delft.

    You're right that allocating road space to segregated cycle lanes won't necessarily be easy, since it has to come from somewhere and in many cases it's not obvious where that should be. Also, it's a lot harder to engineer this kind of thing from our current starting point, since status quo bias is a very powerful thing and any particular road group will resent 'their' space being taken away. I was in Copenhagen recently and noticed that there is relatively less pedestrian space there, but you can imagine that some pedestrians would be very angry if we suggested replacing footpaths with bike paths in London. I think part of the solution is to think more creatively about the kind of road network we want - for example, maybe some streets could be one-way for private vehicles while remaining two-way for buses and bikes.

  3. Yes of course: bigger buses! Now why didn't I think of that?

    Naturally I agree that allocating road space to segregated lanes won't be easy, particularly given our current starting point. But as you say, we ought to start giving much more thought as to what kind of road network we want.

    In response to your comment, I have just posted a blog entitled Daring to redistribute space and means, which looks at how the Europeans set about reallocating road space in favour of the bicycle. I hope you will be interested to check it out. 

    With regards, Simon


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