Wednesday, August 30, 2017

Should we fine cyclists for breaking red lights?

(This was a comment I made in a discussion on Facebook that seemed worth saving. You be the judge.)

I don’t think cyclists should be fined for breaking red lights unless they clearly and avoidably place other people at risk, because it discourages casual cyclists and drives them back to… driving, which is of course much more likely to cause death and injury to others.

But if we insist upon it, then the fine should be proportional to the amount of damage you’re likely to do if you hit someone – this is based on many factors, so probably the most reasonable approach is a fine proportional to kinetic energy, which is the mass of vehicle and rider times the square of their speed.

Let’s do a worked example:

  • 80kg rider + 15kg bike + 5kg gear, travelling at 25km/h (just under 7 m/s)

    • = 0.5 * 100 * (6.944…)^2 = 2,411 joules
  • 80kg driver + 1180kg car (2017 Volkswagen Golf, 1.4L manual), travelling at 30km/h (city centre speed limits, just over 8 m/s)

    • = 0.5 * 1260 * (8.3…)^2 = 43,750 joules
  • 80kg driver + 3365kg van (2012 Ford Transit, 2.0L diesel), travelling at 50km/h

    • = 0.5 * 3445 * (13.8…)^2 = 332,272 joules.

So if we charged people 1 cent per joule of kinetic energy involved in these infractions, it would cost a cyclist €24.11 to break a red light, or €437.50 for a driver of a Golf doing 30, or €3322.72 for a driver of a Transit doing 50.

Or maybe we could acknowledge the fact that cyclists pose so little threat to life compared to cars and vans that we should stop discouraging them from cycling and stop focusing so much effort on blaming them for being “a menace” given that cars travelling at even low speeds carry 20 times as much kinetic energy, take more space, cause more pollution, cause more health problems, damage more bridges and lampposts, and of course cause almost all road deaths.

With this in mind, why are we even having articles in newspapers or radio discussions about the dangers posed by cyclists? Why aren’t our papers and radio discussions filled with appeals to the public to get on their bikes?

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