Considerate Cycling 42: Some Simple Numbers

Figure 1 (source: DfT)

I was interviewed on BBC Radio Bristol recently about the relationship between cyclists and buses in the city. I talked about cyclists’ respect and bus drivers’ professionalism. However, I did suggest that putting cyclists into a shared lane with buses was a bit like putting the meerkats in with the elephants. I also said that compared with goods vehicles and cars, buses were much less of a problem than people might assume.

I was talking about Bristol, nowhere else. I had checked some stats before I went in to talk, so I was fairly happy that what I was saying had some grounding in what had already been recorded and counted. Afterwards I started thinking about whether the simple numbers I had could support the hypothesis that despite their lower numbers, buses and goods vehicles were in some way safer or else more dangerous than cars. I showed the statistics to my son who is a proper mathematician and a data manager by trade. He pointed out my basic problems with standardisation of such different populations and gradually one thing became very clear.

The clear point was that at some level I was trying to find statistical evidence to confirm my prejudice that cars were in some way to blame even though vans, lorries and buses seem so dangerous. I was looking at small differences of probability where none were to be found. What I should have been staring at was Figure 1. The plain fact is that there are over 230,000 cars being kept in Bristol. That’s roughly one car to every 2 people. In comparison, there are just 39,200 goods vehicles, less than 1 van or lorry to every 5 cars. Buses and coaches add up to just 2,400 vehicles, only about one to every 10 cars. What about some more simple numbers? Here is Figure 2

Figure 2 (Source: correspondence with Bristol City Council)

Looking at this, what can we do at a local level to reduce bicycle casualties? What would a modest 10% improvement look like for each vehicle type? Haul back injuries for car-related incidents and we would avoid 47 injuries. 10% of the goods vehicle totalĀ  would save 3. 10% of bus-related injuries would save 1.

So what might reduce car-related injuries? Some more simple numbers offer a clue:

Figure 3 (Source: DfT)

The number of cars in Bristol has gone from 184,019 in 2004 to 231,853 in 2013. That’s a 26% increase in what was already a large number. Most of that has been in the last four years.

Here’s a photograph of a Bristol street. Recent political turmoil in the City has raged over Mayor George Ferguson’s attempt to restrict car parking and reduce speed limits.

Picture 1

What does it look like to you? What, if you had the power, would you want to control if a better and safer city was your aim? What would you prioritise if you wanted to reduce road traffic casualties and improve public health? How you do it is up to you, but I would say that the answer stares us in the face.

 

 

 

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