where are the speedo-watching crashes?


Here are the two petitions to look at

Speeders: Scrap the 20mph limit in Bristol and restore common sense  now at 8045
Keepers: Keep and extend 20mph limits now at 1680

One claim in the Speeders' petition is
"roads will only be made more dangerous with frustrated drivers and people watching the speedo rather than where they're going!"
We haven't noticed that ourselves, as we have a special speed limiter in our car called "the gear stick". Put it into "speed band 3", or "3rd gear" as it is sometimes known and it burbles along quite happily at 20-24mph, except in the special case that someone drives so close that you can see the driver's nostril hair and you slowly lift your foot of the accelerator to drop to precisely 19 mph just to see the expression on the driver's face in your rear view mirror.

Anyway, it may be that the speed petitioners don't have manual transmissions, or are somehow unable to determine road speed, and do have to look at the speedo all the time.

This is something we can test now that the central 20 mph zone is over a year old. All we have to do is look at the data.

One irony here is that if they do occur, the fact that they will take place at 20 mph means the police aren't likely to get involved. Any crash involving pedestrian, cyclist or stationary object will be less likely than at 30 mph to injure anyone, so they may not get called out. Indeed, even the insurance companies may not get a look in if people care about their no claims discount. head-on collisions will still have 40-50 mph of energy, so are more likely to show up. This means official data sources: —police and insurance— may show a reduction in RTCs even if there has been an increase in RTC events.

We ask the speeders, then: where are the speedo-watching crashes?
  1. How many crashes in 20 mph zone have you personally been involved in where you or another participant was looking at the speedo at the time?
  2. Have you heard of any such crashes —and do you have the contact details for us to follow up on this?
  3. Is there any other evidence for an speedo-watching crashes in the central bristol zone?
We've had the zone for 18 months now, with millions of journeys in it by now. If speedo-watching crashes are a risk in 20 mph zones, we should have seen some. 

If we don't have the any signs of speedo-watching crashes, then, it could be due to
  1. They are happening, but the massive lower energies in the collisions cause them to be unreported
  2. That whole claim about "watching speedos causes crashes" is bollocks.
#2 is the null hypothesis: 20 mph limits do not cause speedo-watching crashes, is the one which has to be disproved to a significant degree of statistical confidence before it can be believed.

We put it to the speeders then: show us the data.

Now, assuming, on the off-chance that there is the data, that speedo-watching does cause crashes, hence 20 mph zones are more hazardous than 30 mph zones, why do the petitioners still propose lower limits by schools?




Either 20 mph zones are more dangerous due to speedo-watching or 20 mph zones are safer round schools.

So if that claim "20 mph is more dangerous" isn't utter bollocks, then, if the speed campaigners really believed it, they should be pushing for 30 mph zones round schools "for the children".

Speeders: show us the data —you've had 18 months to collect it.

(photo: kid scootering to school outside Christchurch School, Clifton, pre-RPZ)