Scripts

Thursday 26 June 2014

Helmets are a Distraction

In my opinion the discussion surrounding helmets and the obsession by some calling for them to be mandatory is a massive distraction from the real issues concerning cycle safety. In countries like the Netherlands virtually no one uses helmets and yet the rate of deaths and injuries compared to the UK is practically an order of magnitude lower.

It is blindingly obvious that real safety will come from providing proper dedicated Dutch style  #space4cycling and improving the behaviour of motorists around cyclists. Risk of injury imo is due to frequency of errant interactions between motorists and cyclists, and cyclists being forced to use inappropriate roads. i.e the more close passes you experience the more likely you are to get injured, and similarly cycling on busy/fast roads is riskier than using a good quality well designed cycle-way.

If we can improve the above situations then safety will increase considerably, and that imo would dwarf the small numbers that might be saved be by forcing everyone to use a helmet. No country has yet demonstrated a plausible or significant increase in safety with mandatory helmets*.

Below is an ad-hoc calculator to estimate how many would be "saved" by forcing people to wear helmets if helmets really did protect against serious injuries, and how many would be "saved" by improving overall safety through #space4cycling and/or driver behaviour.

Current situation:
Percentage of journeys by bike
Percentage of people using helmets
Current deaths
Current serious injuries

Magic plastic hats:
Percentage that would be "saved" by using a helmet

#Space4cycling and improved road conditions
Safety Multiplier, how much safer it could be

What if more people cycled (like in Holland):
Percentage of journeys by bike

Injury rate vs cycling rate:

"Safety in numbers" fudge factor
Results:

Tuesday 17 June 2014

Cyclist Driving Sight Distance Calculator

If you are driving and have to slow down behind a cyclist because it is not safe to overtake, how much sight-distance is required?

Braking fraction 0.7
      
1.0 is hard braking, less 0.5 soft braking
Thinking Time 0.5
      
in seconds


Visibility distance (metres) needed for Bike Speeds (mph) vs Car Speeds (mph)

Braking fraction, 1.0 is emergency stop braking based on approx rates from Highway Code. Friction=0.7
Car speed is from left to right, bike speeds increasing downwards:
Thinking times: competent reaction times are usually mush less than 1.0s
Ref: http://en.wikipedia.org/wiki/Braking_distance