Tuesday, 6 September 2016

Cyclists vs. Runners

This is another of those 'belt it out before work' type posts.

I spotted a tweet thats been picked up by bigger feeds like ukrunchat, and its worth a ponder:

The answer is simple enough really. Lots of cycle facilities are rather mediocre 'shared use' pavement routes. Sometimes they're better signposted from the road than they are from the pavement, so if you primarily use the pavement at one of these locations you may not even have seen such signs. Its also very often the case that this provision suddenly ends with no notice - so you're riding perfectly legally down a shared use path, then you're suddenly riding illegally, but with no way of knowing this.

But cyclists do break the law and go on the pavement to avoid frankly terrifying road conditions - and this is acknowledged in guidance originally issued alongside the capacity to issue fixed penalty notices. To paraphrase - chill out, the cyclist is just trying not to get killed.

But lets take a step back and, for a moment, just compare the risks brought by each. Remember, we can determine the kinetic energy of an object simply enough, half mass times velocity squared, and a cyclist at 15mph has about 2000 J. 

A runner, going shall we say 8mph and unencumbered by the mass of a bicycle so, shall we say 80kg, thats a little over 500 J. Yes, the cyclist can bring more bang in a collision, by about four times - not by the orders of magnitude difference we see between a cyclist or pedestrian and a car. Lets also say, though, that a cyclist on the pavement is going more slowly than a cyclist on the road would be, a fair assumption considering how bumpy and congested with street furniture our pavements have become. At that speed we're only looking at about 1250 J - two and a half times more energy - we're down to the kind of differences where the specific type of collision becomes very important in determining what the real risks are.

We really should reflect that while understanding the numbers still show its better for cyclists and runners not to mix on pavements, that there are very few injuries thus caused is a fair reflection of the fact that the actual risk of this is low. Do you want cyclists off the pavement so you can run there without worrying about it? Great, I'd like that too - what you need to do is pester your local authorities and central government to build segregated infrastructure that facilitates this.

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