Tuesday, January 28, 2014

The Mists and the Washes and cycling statistics

Monday, 20th January 2014: At this time of year you have to be careful, the low-lying sun seems to allow some drivers to speed along and then blame the sun if they crash into a cyclist. I was taught that drivers had to drive more slowly, in accordance with the conditions prevailing.

At this time of year we are also accustomed to crackdowns on cyclist without lights. It seems that cyclists without lights are a danger to themselves and everybody else. Although there seems to be little quantification of data that supports this idea. Check out this excellent post – “Visibility in context” for a bit of an eye-opener on the subject. Is it just me or is it that PCSOs always seem to be the ones doing the crackdowns on cyclists?

I wonder who is it that decides what out traffic laws should be doing and then ensuring they do just that?  certainly the DTI pumps out lots of statistics and considers all sorts of aspects concerning transport.  However who checks to ensure that our traffic laws are doing the right thing. For instance we have speed limits – although those limits are both limits and not limits.  We have ACPO publishing guidelines with leeway regarding the limits and reasons why there should be tolerance. One example being if a road looks fast and the signs are very good! Another reason appears to be if it is impractical.

There are many drivers who would of course consider themselves safe drivers and that going a little above the speed limit does not cause any significant additional danger. There are others who would consider that lower speed limits are “more dangerous” and that driving under the speed limit is also dangerous.

An RAC survey suggested that 92% of drivers consider themselves to be law-abiding, yet 65% admit breaking the 70mph speed limit on motorways. If so many people do it why is it wrong?

Well for my take on the matter let’s look at a recent Times article concerning motoring and cycling accidents: “Motorists and cyclists create army of walking wounded”. Now let me quite the first few sentences:

Motor vehicles kill five times more pedestrians than cyclists, but figures show risk of serious injury is similar relative to distance travelled

Cyclists are almost as likely as drivers to cause serious injury to pedestrians, analysis of official figures shows.

The data, revealed by annual road casualty statistics, provoked calls for responsible cycling and the construction of dedicated facilities to keep cyclists out of conflict with other road users.

When serious injuries are measured as a proportion of distance travelled, cyclists injured 21 pedestrians per billion km travelled in 2012 compared with 24 pedestrians injured by drivers.

Read that and it looks like carnage on the pavements – whew, those bicycles must be really dangerous eh.

Yet later on we see that in 2012 one pedestrian was killed by a cyclist and 78 seriously injured, whereas 253 pedestrians were killed by drivers in urban areas and 4,426 were seriously injured.

I can immediately think of several issues here.

  1. Why present the data as injuries per billion Km travelled?  It makes bicycles appear more dangerous, yet actual deaths and injuries caused by cyclists are a fraction (0.4%/6%) of those caused by motor vehicles. Surely what really matters is the numbers of people killed and seriously injured.
  2. This ignores the fact that much of the motoring is done on roads with very few pedestrians – motorways, dual-carriageways etc. Whereas cyclists and pedestrians are frequently intermingled.
  3. The definition of Seriously injured is very wide and can vary in the UK. 
  4. A major factor determining the seriousness of injury in an accident is the energy in the collision and the associated acceleration/deceleration. What would you rather be hit by a car at 20mph or a cyclist at 20mph.  Both would be unpleasant – but the energy in the cycling crash is significantly lower.  (The Kinetic energy is 1/2 mass * velocity2 ) So even at the same speed the energy is likely to be around 15 times as much in the car accident. Of course if the vehicle is a bus or a lorry or even a van…
  5. If bicycles are that dangerous why do so many Councils positively encourage shared-use paths?
  6. We need to consider how often something occurs, the probability of an accident occurring and the consequences if such an accident occurs. Whilst the probability of an accident occurring from one instance of speeding might be small, speeding occurs so often that an accident somewhere becomes very likely. (There is the additional factor that increased speed reduces the thinking time and the energy of a collision.)

Sorry I just felt that the Times article was statistical diarrhoea – with the main headline being bollocks. The number of walking wounded caused by cyclist/pedestrian accidents in 2012 was more like a small battalion. 

What I do agree with is that motor vehicles are way more dangerous than pedestrians or cyclists. Cyclists are having to share the roads with motor vehicles or share the paths with pedestrians. We need to develop cycling specific infrastructure, especially in congested cities.

Fortunately accidents like this – “Cyclist hit by flying shed” are very rare. Unfortunately scenes where cyclists get attacked are becoming less rare. A person with such a short fuse on his/her temper should not be permitted to drive IMHO. (Yes in this case it was the passenger – but the point remains the same.)

Back to another ride – the advantage of the short number of daylight hours is that there is more opportunity to get pictures of the sun low in the sky.

Low sun over a water logged field near White Fen

This field is just across the track from the last one – dry and even the sky looks totally different.

Field next to White Fen

Upware Washes

There are quite a few areas where people live alongside floodplains. The Fens were waterlogged not so many years ago. The trouble is were have pressure to build more houses, which can lead to land more prone to flooding being used. We have changing weather and we have more urbanisation which can put pressure on our existing waterways and drainage channels.

The Cambridge Guided Busway heads through a floodplain and various estimates were made for how often the cycle track alongside the raised busway track were likely to be flooded each year. It seems to me that those calculations woefully underestimated the likely flooding.

Willows and Washes of the River Cam – Upware

Upware Washes

Bird Tower – Wicken Fen

Setting Sun – Fens

As the sun set mist began to form/

Mists forming in the Fens

These Mists seem to be coming from Swaffham Bulbeck Lode

Mists rolling across the Fens

Mists rolling across the Fens

Once I was the other side of the Lode in White Fen the mists had gone!

White Fen

No comments:

Post a Comment

Post a Comment