Monday, 6 March 2017

Fact checking the recent Hackney Cycling Campaign road safety press release

I was intrigued when the @Hackney_cycling twitter account announced: "Is there any safety in numbers?" I clicked on the link to their website that says:

"New analysis of police injury data known as Stats19 carried out for Hackney Cyclists by Dr. Rachel Aldred shows worrying trends in the borough." 
And from Dr. Aldred:

‘Clearly cycling in Hackney has grown during this period, perhaps roughly doubling, but it’s a concern that there doesn’t seem to be much of a ‘safety in numbers’ effect for cyclists – in other words it hasn’t got much safer per trip, as cycling has gone up.’
The full statement taken from the Hackney Cycling website is reproduced at the bottom of this page.

But the Hackney Cycling Campaign analysis is partial and misleading. So here is a fact check of Dr. Aldred's 'analysis'. 

The claim is that cycle casualties went up in Hackney between 2005 and 2015 along with the numbers of cyclists, but that safety had not improved 'per trip'. The analysis states that there were 134 cycling casualties in Hackney in 2005 and that this went up to 250 in 2015. Dr. Aldred's figure for 2015 is one out, it is actually 249, however, this equates to an 86% rise between 2005 and 2015.

These figures are reliable, but care should be exercised in their use. The number of casualties can vary quite markedly from one year to the next and picking out two years figures to compare can be misleading. Looking at the trends and averages over three years is both more meaningful and more usual. For the readers benefit the graph below shows the figures for casualties in Hackney between 2001 and 2015.



All Hackney cycling casualties, from minor injur to fatalities, against year
So the numerator is correct. But, how did Dr. Aldred arrive at the denominator in the 'analysis'? This is described in the press release:
"Clearly cycling in Hackney has grown during this period, perhaps roughly doubling..."
So there we have it, the denominator in the equation is made upThe 'analysis' turns out to be a guess: 
(134 ÷ 249) ÷ (perhaps roughly doubling)
But can we do better than Dr Aldred, or at least understand the complexities? I think so.

There is no reliable cycle volume data, particularly at a London borough level. Transport for London has London wide data, but there is very great variability between boroughs and Hackney is an outlier in cycle statistics. The Department for Transport (DfT)  publish some data for Hackney, but it is not very accurate at a borough level because it is a small sample count of cycles and only on main roads.

The only reliable statistic for the increase in cycling in Hackney is the Census figures for 'Method of travel to work'. But even these figures are limited to travel to work and they are now quite dated. The figures that are available are for 2001 and 2011. 

So, below is the same calculation that Dr Aldred has done, but taking the years that have a reliable statistic for both cycling levels as well as casualties. Between 2001 and 2011 in Hackney casualties rose from 134 to 259 (93%). In the same period cycle to work Census figures rose proportionately much more, from 4940 to 17312 (250%). 
(259 ÷ 134) ÷ (17312 ÷ 4940) = 0.55
In conclusion. Over the only period for which there is a reliable and comparable statistic for growth in cycling (2001 to 2011) the casualty rate has dropped markedly. 

For the period Dr Aldred has 'analysed' there are no cycle volume figures and so Dr Aldred has guessed what the growth in cycling might be. Can such a poor analysis be regarded as good practice in either the academic or policy development milieus?

_________________________________________________________________________




Taken from the Hackney Cycling Campaign website:


IS THERE REALLY ‘SAFETY IN NUMBERS’?

JONO KENYONFEBRUARY 27

New analysis of police injury data known as Stats19 carried out for Hackney Cyclists by Dr. Rachel Aldred shows worrying trends in the borough. Hit and runs are on the increase, and are now happening at a rate of one every two days. While 11% – just over one in ten – of all injury collisions across Britain involve a hit and run vehicle, the figure’s higher in London (15%, or around one in seven) and an even higher one in five in Hackney. And while one in five sounds high enough, it’s one in four for collisions where a pedestrian or cyclist is injured.
Jono Kenyon, Co-ordinator of Hackney Cyclists, says ‘One of our three ‘asks’ for Hackney mayoral candidates was a higher priority for roads traffic policing. Hundreds of people are injured on Hackney’s roads every year while walking and cycling. Road traffic offences, from close passes to hit and runs, need to be tackled to help make our roads safer for everyone.’
Since 2005, injuries to cyclists to Hackney have increased, and although numbers have been falling in recent years, in 2015 there were almost twice as many cyclists injured in Hackney as there were in 2005 (250 vs. 134). Over the same period pedestrian injuries have been roughly stable but car and taxi occupant injuries have decreased. Dr. Aldred comments ‘Clearly cycling in Hackney has grown during this period, perhaps roughly doubling, but it’s a concern that there doesn’t seem to be much of a ‘safety in numbers’ effect for cyclists – in other words it hasn’t got much safer per trip, as cycling has gone up.’

 Join us this Wednesday 1st March to hear more about these issues and see what Hackney Cycling is proposing to ask for in terms of better protection for our communities:


No comments:

Post a comment