Road deaths increase for the first time in a decade

[Feline]

Deaths on bikes and motorbikes are down, but serious injuries are up, so not really good news.

That might reflect improved A&E techniques and protocols improving survival rates. I would hazard a guess that any declining rates of death have been greatly affected by this in the last decade or so. Things like ultrasound fast-scans for internal bleeding becoming standard practice in trauma cases really improve the chances of a victim making it when they previously might not have done. Yay for the medics, I say. It skews the figures though if they are claiming fewer deaths are down to better road safety.

[simonp]

See graph on page 22 of this report from 2010:

http://assets.dft.gov.uk/statistics/releases/road-accidents-and-safety-annual-report-2010/rrcgb2010-complete.pdf

The numbers killed plateaued for several years while serious and slight injuries dropped, then there was a significant drop in K to 2010 basically bringing K back into line with SI's trend.

[Wowbagger]

http://www.guardian.co.uk/commentisfree/2012/jun/29/more-die-roads-car-king

Splendid piece on this by Jenny Jones.

[rogerzilla]

I'd need to see the casualty rates on a per km or per hour basis to make a judgement.  Otherwise it's all conjecture.

[spindrift]

And only last night, the Mayor of London, was telling an audience at a debate broadcast on radio that cycling was getting safer.

 Yet, even Transport for London admits that the cycling casualty numbers are 'statistically significant'.The TfL announcement points out that the number of people cycling on London's trunk roads has increased 173% since 2001, so a 36% increase in serious casualties is represented as an improvement. As one commentator points out below, the likely increase in cycle trips in 2011 vs 2010 is probably around 5-6% (the official figures haven't been released yet) against a slightly smaller increase the previous year. Whichever way you look at it, the rate of serious injuries to people riding bikes seems to be growing faster than the growth rate in trips made by bike.

http://cyclelondoncity.blogspot.co.uk/2012/06/33-more-pedestrians-60-more-cyclists.html

[David Martin]

I remain unconvinced that the change in death count is anything more than statistical noise when set against the ride in cycling trips. Care to publish the figures and p-values for the claims of significance?

Easy enough to make political capital over absolute numbers, but a sound analysis requires more.

[spindrift]

I remain unconvinced that the change in death count is anything more than statistical noise when set against the ride in cycling trips. Care to publish the figures and p-values for the claims of significance?

Easy enough to make political capital over absolute numbers, but a sound analysis requires more.

Why do people respond to posts they haven't bothered to read?

The TfL announcement points out that the number of people cycling on London's trunk roads has increased 173% since 2001, so a 36% increase in serious casualties is represented as an improvement. As one commentator points out below, the likely increase in cycle trips in 2011 vs 2010 is probably around 5-6% (the official figures haven't been released yet) against a slightly smaller increase the previous year. Whichever way you look at it, the rate of serious injuries to people riding bikes seems to be growing faster than the growth rate in trips made by bike.

What's more, London's roads are getting worse for everyone. Unless you're in a car. There were 2% FEWER casualties among car occupants in London last year versus the previous year. Look at the figures for pedestrians, though, and the change is shocking. 77 pedestrians were killed on London's roads last year, up 33% on 2010. That's outrageous.

Ibid

Bike traffic in London has increased. By approximately 4-6% per annum. And yet the casualty rates have not decreased. They've increased too - seemingly far faster than the growth in the number of bike trips.

[David Martin]

'far faster' based on one years figures on a background of rising participation.

36% increase in casualties vs 73% increase in participation indicates an improvement in safety.

If you would care to calculate the likelihood of a random fluctuation in small numbers being responsible for the apparent rate increase then you may be correct in claiming 'far faster', or 'significant increase'. Without that it is quite probably just normal random fluctuation.

So lets look at some numbers in context. This will give an idea of the longer term variability.

Year                Deaths           Serious injuries       Bike trips*     Rate**
2002               20                    394                              300                  0.36
2003               19                    421                              320                   0.36
2004               8                      332                              330                  0.28
2005               21                    351                              390                  0.25
2006               19                    373                             420                  0.24
2007               15                    446                             420                  0.29
2008               15                    430                             440                  0.27
2009               13                    420                             470                  0.24
2010               10                    457                             490                  0.26
2011                16                    Not available yet      Not available yet

Rate is KSI per 100,000 trips. In other words cycling twice daily in London you will be pedalling for over 500 years before you have a serious injury (one requiring hospital attention).

The conclusion then is not that 2011 is unusually high, but that 2010 is unusually low, especially given the increase in trips. We see a big and sustained reduction in 2003/4 but nothing out of the ordinary since then.

So, real numbers. I could count the significance and work out the chance of getting figures like that by chance, but ICBA as just by eye they will be much larger than any kind of sensible significance threshold.

[David Martin]

I was bored so I ran the numbers for individual years and aggregating successive years. If p=0.05 (two sigma) is taken as a measure of significance, and projecting journey numbers on the same trend as previous years (to 515, a 5% increase) then 2011 is not significantly different to 2010, despite 2010 being lower than expected (but not significantly so.) The only significant changes are 2003-2004 and 2004-2005.

So yes, more can be done, but no, there is not a sudden widespread carnage in London. Cycling remains a reasonably safe and fun way to get about, though it can have the perception of danger about it.

[gordon taylor]

^^^^^^^^^^  This. 
The statistics over time are complex. To grab one figure from one year and use it to bash a single issue (London bus lane regulations) and blame a single man (Boris) is a tactic best left for politicians on TV. IMHO.

The DfT do a vast amount of research into the sources and reliability of these statistics. To me, the most interesting part of the whole release is in the final paragraphs:

"However, it has long been known that a
considerable proportion of non-fatal casualties are not known to the police, as hospital, survey and
compensation claims data all indicate a higher number of casualties than police accident data
would suggest.
Our best estimate produced in 2011, derived primarily from National Travel Survey (NTS) data, is
that the total number of road casualties in Great Britain each year, including those not reported to
police, is within the range 660 thousand to 800 thousand with a central estimate of 730 thousand. "

So - the Police figures used in this report indicate around 200,000 road casualties in 2011. The real figure is probably around three or four times greater than that. Wow!

I recommend some detailed further reading to all posters:

http://assets.dft.gov.uk/statistics/releases/reported-road-casualties-gb-main-results-2011/reported-road-casualties-in-great-britain-main-results-2011.pdf

http://www.dft.gov.uk/statistics/releases/reported-road-casualties-gb-main-results-2011

[spindrift]

http://www.standard.co.uk/news/london/london-pedestrian-deaths-and-cycle-injuries-soar-7899270.html

As the article states, there is a year on year increase of cycling on main roads of around 9%.

Currently the increase in cycling on all roads for 2011 from 2010 is not known.

 However, from 2008-2009 there was a 5% increase, from 2009 to 2010 there was a 5.9% increase (http://www.tfl.gov.uk/assets/downloads/corporate/travel-in-london-report-4.pdf).

So, to account for the 22% increase in KSI's to the increase in cycling for the year, there would have to have been an unprecedented percentage increase in cycling during 2011 compared to previous years. I could be proved wrong but I doubt this is the case.

In addition, we must not forget the huge increase in pedestrian KSI's. Can we assume people are walking more to account for this? Or are there other factors involved such as the removal of pedestrian crossings?