Contributory factors in cyclist casualties

Mark King of the Guardian writes:

DfT statistics reveal that the biggest single contributory factor in cycle deaths is the cyclist failing to look properly (25% of fatalities), followed by failing to judge the other person's path or speed (10%), the cyclist entering the road from the pavement (8%), and careless or reckless behaviour (8%).

This gives the impression that errors by cyclists themselves are the dominant factors contributing to cyclist deaths. And that would be the wrong impression, because (a) the figures quoted refer to all accidents, not just fatal ones, and (b) by definition they exclude any actions of motorists or other non-cyclists. The rest of this post goes into these reasons in more detail.

The statistics Mark King is referring to are from DfT's 2010 road casualties report here. Table RAS50005 in that report shows 'Contributory factors reported for vehicles in reported accidents' and under 'Pedal cycles' the top 'Contributory factor attributed to vehicle' is indeed 'Failed to look properly' at 25% of the total number of cases. But these figures don't mean what Mark King thinks they mean.

First of all, it should be fairly clear that this table doesn't just deal with fatal accidents. There are 11,929 incidents reported under the 'Pedal cycle' category, and I think most people know that there weren't 11,929 cycling fatalities in 2010. So that's one rather important mistake.

The second issue is more subtle but is important to understand. As the DfT report makes clear in the paragraph directly above the table in question, these figures are about the contributory factors attributed to vehicles involved in accidents, not the factors behind each accident. Put another way, the table describes what vehicles of each type did, not what caused casualties of each type. So the 168,990 figure at the end of the 'Car' column indicates the number of cars involved in reported collisions, not the number of car driver/passenger casualties (the fact that the figure is labelled as 'Number of vehicles' and not 'Number of casualties' is a clue).

So the figures quoted don't show all the factors contributing to cyclist casualties, but only what cyclists did in collisions involving cyclists, which will include a number of collisions where there were no cyclist casualties at all (e.g. involving pedestrians).

Unfortunately DfT don't seem to publish statistics showing the contributory factors to cycling casualties. Fortunately, the Transport Research Laboratory published a report in 2009 which does just this (in fact, Mark King mentions it in his article).

Briefly, the TRL report lists 430 collisions where a cyclist was killed (between 2005 and 2007), of which 354 were reported as involving a collision with another vehicle (figure 7-2). In 183 of these fatal collisions there were contributory factors attributed to cyclists, of which 31% (which equates to 57) involved the cyclist failing to look properly (table 7-4). 57 is 13% of 430, so you can probably say that cyclists failing to look properly was reported as a contributory factor in 13% of cyclist fatalities, not 25% as Mark King says. It's also worth noting that figure 7-6 shows that drivers failing to look properly was reported as a contributory factor in an almost identical number of cases (44% of the 131 cycle fatalities where a contributory factor was attributed to drivers). As the TRL report says, "attribution is split fairly equally between the cyclist and driver/rider of the motorised vehicle".

Finally, it is really important to understand that these figures are just based on what police officers subjectively reported when they were called to the scene of a collision. As the TRL report states very clearly, "this does not necessarily mean that the cyclist or other road user was in fact responsible". The media and the rest of us should bear that in mind when using these figures.

Some estimated cycling casualty rates for London and other cities (a work in progress)

Update! I've added figures for Helsinki (thanks Tommi) and Vienna (from here). Details are in the accompanying spreadsheet.

It would be very interesting and useful to have some statistics allowing us to compare the safety of cycling between different cities around the world, but this kind of thing is very hard to come by. As far as I can see it's nobody's job to collect statistics from cities in different countries, so at present nobody does it. In some places, individual city governments/authorities/mayoralties do collect and publish statistics, but only some of these are comparable with other cities. This post is the start of an attempt to collect together figures which we can use to compare London to other cities in terms of cycling casualty rates.

Please note, these figures are just initial estimates, cobbled together from available sources, some of which may not be correct. I would very much welcome any better information, and especially any similar information for other cities. If there's something here you think is wrong, instead of getting annoyed why not send me a correction?

The table and chart below show some summary information on distance cycled, cycle casualties, and the cycling casualty rate (per distance cycled) in Amsterdam, Copenhagen, Berlin and London (and now Helsinki and Vienna). This spreadsheet gives more detail on the sources, which where possible are official statistics but in a couple of cases (e.g. the total distance cycled in Amsterdam per day) are not.

	Amsterdam 2009	Copenhagen 2010	Vienna 2008	Berlin 2009	Helsinki 2008	London 2010
KM cycled per day (m km)	2.2	1.21	-	4.82	0.82	1.73
KM cycled per year (hundred millions of km)	8.03	4.05	2.76	17.58	2.98	6.32
KSI per year	104	92	71	538	170	467
KSI per 100m km per year	13	23	26	30.61	57	74
Million km per KSI	7.7	4.4	3.9	3.27	1.8	1.4

For the casualty rate I've used the number of cyclists killed or seriously injured per 100 million kilometers cycled per day in each city. I know the casualty rate per km isn't very good for comparing the relative risks of different modes of transport where the average trip length is very different, but it should be fine for comparing cycling casualty rates between cities. I guess you could also calculate a casualty rate per trip, but then you get into how to define a 'trip', which isn't as straightforward as you might think.

I should probably say that this certainly isn't an attempt to make London look like a dangerous place to cycle. While I think it could certainly improve on that score, I'm sure there are many, many cities with worse casualty rates. But most of them probably don't collect any robust, comparable statistics. There is a selection bias of sorts at work here, in that it is generally those places which have fairly strong cycling cultures which collect the best statistics on cycling.

I'd love to add some more cities, but comparable data is hard to come by. I looked around for data from Paris and found absolutely nothing, while I couldn't find any statistics on distance cycled in New York. Any help on these two or on any other cities would be really appreciated.

Another important caveat: In each case I've taken the city borders as read. Measuring the extent of a city is notoriously difficult, everyone does it a bit differently, and in most cases statistics are just based on administrative borders rather than any 'functional area'. So it maybe that with these statistics each city is defined differently, for example with some including suburbs and some not. I know that the London area used here includes a lot of suburbs, but I don't know whether the other cities do. I'd be interested to hear from anyone who does and who thinks this might significantly affect the answers.

Cycling trends in London since 2001

A couple of weeks ago I wrote about how cycling to work became more common in Inner London and less common in Outer London between 1971 and 2001. This provoked an excellent post on the 'cycle of decline' in Outer London from David Arditti (see also here).

Now I'm going to look at what information we have on more recent cycling trends. The results of the 2011 Census won't be out for another year or thereabouts, so instead I'm drawing on the Department for Transport's National Road Traffic Survey data, which you can access here. DfT count the average daily flow of traffic on major roads throughout the country on a yearly basis, and there's more detail on how it works here. I used some of this data for a previous post on trends in cycling at Kings Cross.

DfT's data includes traffic counts at nearly 1,900 count points on major roads in London between 1999 and 2010, with a few gaps here and there. The usual major categories of motor vehicle are counted, as are cyclists. And by averaging all the counts in a particular borough you can get an idea of the trends at borough level, with the caveat that the data doesn't cover minor roads.

The first chart below shows the trend in DfT's average daily count of cycles between 2001 and 2010 in Central London (Westminster and the City of London), the rest of Inner London and Outer London.

So what we see is an increasing divergence between the inner city and the outer suburbs over the last decade. The average cycle count increased by about three-quarters in Central London and doubled in Inner London, but rose by only about a third (122 to 159) in Outer London.

The chart below (click to embiggen) gives some borough-level data, showing the percentage change in average daily cyclists count by borough, with the Inner London boroughs in blue and the Outer London in red.

Update: I have added another chart, this time showing cycling's share of total traffic in each borough in 2001 and 2010. This shows that in the case of some boroughs (like Barnet) which have seen fairly high proportional increases the actual level of cycling (compared to overall traffic) is still quite low.

Again there's a stark contrast between Inner and Outer London boroughs, though cycling increased in nearly every borough over the period. Barnet and Greenwich saw relatively high increases in cycling for Outer London boroughs, while Westminster had a relatively low increase for a central borough (contrast with the City).

My post on Census data included a chart which identified a fairly close relationship between increases in car use and declines in cycling. The chart below plots the percentage point change in cars' share of average traffic flows versus the change in cycling's share, at borough level, and this time the relationship looks even stronger, with areas where cycling increased the most also seeing the biggest falls in car traffic (note, 'car' traffic here doesn't include goods vehicles). Those boroughs in the top left corner (with both big decreases in car traffic and big increases in cycling) are City, Lambeth, Southwark, Islington and Camden. The two Inner London boroughs where the share of car traffic has risen are Newham and Tower Hamlets.

Finally, here are a couple of charts which show the change in the share of cycling and car traffic at each count point, arranged by distance in kilometres from the centre of London (Trafalgar Square, to be exact). There's a good bit of noise at the level of individual count points, but the overall patterns are still fairly clear - the roads closest to Central London generally saw the largest increase in cycling's share of total traffic and the biggest drop in car traffic's share.

The urbanisation of cycling in London

I've just published a post over at LondonTransportData about what I think are some very interesting trends in the proportion of people who cycle to work in London. The data is from four successive Censuses, 1971 to 2001, and at London level it looks like this:

Not all that interesting, but go below regional level and you get this.

What we're seeing here is that whereas cycling to work was twice as common in Outer London as in Inner London in 1971, by 2001 it was the other way around. Rates of cycling to work fell for 40 years in Outer London and rose in Inner London.

Here's the pattern at borough level:

As I say on LTD, two things stand out here. First, boroughs with relatively high cycling rates in 1971 tended to see decreases over the next 30 years. Secondly, Inner London boroughs nearly all saw an increase while Outer London boroughs nearly all saw a fall. The only Inner London borough that didn’t increase its cycling rate over this period was Newham.

On the basis of this data it looks like cycling in London changed from a mostly suburban to a mostly urban phenomenon over the course of a few decades, although it's worth bearing in mind that it remained very much a minority pursuit in both areas throughout the period. It would be nice to know why this change happened, and I'd be interested to hear any theories anybody has, bearing in mind that it all happened the introduction of the congestion charge, and mostly before we had much in the way of red routes, or 20mph zones.

Here a are a few theories on what might have caused this turnaround:

Traffic: There was less motor vehicle traffic in both Inner and Outer London in 1971 than in 2001. Perhaps as a result cycling conditions in the suburbs were relatively benign, as there was more space on the roads than in the inner city. But as traffic increased, two things happened: in Inner London, rising congestion made commuting by car painfully slow, so the bike became a more attractive option for some. But in Outer London, increasing traffic just increased the collision threat faced by cyclists, and most of them stopped as a result.

The Census data provides some tentative support for this hypothesis: as the chart below shows, car commuting increased much more in Outer London over the 40 year period, and across London there was a strong negative relationship between the change in car commuting and the change in cycle commuting.

Infrastructure: Maybe it was all about changes in the provision of cycling facilities in Inner and Outer London, with cycle lanes and paths being added in Inner London and taken away in Outer. Or maybe there's a link with the first theory, in that the lack of infrastructure in Outer London didn't matter when there wasn't much traffic but became a deterrent when there was.

Labour market: Maybe it was the pattern of commuting that changed, with longer journeys less suited to the bike becoming the norm in Outer London over time. I'm sure there's data out there on trends in commute lengths, but it might be hard to disentangle cause from effect.

Of course, it could be a mix of the three, or something else altogether. But I think anyone interested in growing cycling in London needs to think about why this happened. I'd also love to hear whether there's any evidence of a similar pattern in other cities.

Cycling trends at Kings Cross

Following the tragic but sadly all too predictable death of Min Joo Lee at Kings Cross a fortnight ago, some people are talking about a charge of corporate manslaughter against TfL.

Something you sometimes hear in debates around the rising number of cycling casualties is that the number of people cycling in central London is growing quickly, so even with a falling accident rate you might well see more casualties. That's true enough as a statement of fact, but I think you need to think through the implications. If people are autonomously choosing to cycle more despite its relatively high risk, do you leave the road network as it is and accept the increased level of casualties, or do you decide that the roads need to change to accommodate a changing mix of users?

Some figures on trends in cycling around Kings Cross might help illustrate the point. Here are counts of the number of cyclists on four main roads around the junction where Min Joo Lee died, carried out by DfT every year since 1999 and available here.

And here are trends in cyclists as a proportion of total traffic on the same roads, from the same source:

Cycling in this area seems to be growing quickly in both absolute and relative terms. I suspect even TfL would admit that this isn't due to the area becoming much more cycle friendly in recent years. It's more likely to be driven by rising public transport fares and the congestion charge making other modes of transport less attractive.

But whatever the reason, it's plain that people are cycling more in central London, even around objectively awful junctions like Kings Cross. That shouldn't be seen as an excuse for higher numbers of casualties, but as a powerful argument for driving down the collision rate faster than before.

Forecasting cycling levels on Blackfriars Bridge

Transport for London have published, following a Freedom of Information request, the analysis used to make its forecasts for the modal share of people using the new Blackfriars junction when it opens in 2012. Futilitarian has already critiqued much of the methodology, but I just want to focus on the forecast of cycling levels in 2012, which (as Futilitarian says) seems very much on the low side.

TfL forecast that cyclists will make up 6% of people using the junction in 2012:

Their explanatory note says the cycling figures were derived as follows:

• In 2007/08 there were 1173 cyclists. This is based on JMP’S January 2007 cycle counts which have been uplifted by 17% to reflect seasonal differences in cycle numbers.
• In 2012 there are assumed to be 1666 cyclists. Cycling numbers uplifted by 42%, based on modal share changes reported 2007-2009 in Travel in London Report 3.

Let's accept the 2007/08 figure. What then is the best basis for forecasting growth to 2012? TfL seem to have looked at the number of cycling trips across the whole of London in 2007 and 2009, in table 2.1 of the Travel in London report here. The table says there were 0.4m cycling trips in 2007 and 0.5m in 2009, which is consistent with a 16% increase which would gross up to 42% over five years.

But other data presented in the same report suggest that the cycling trend in London as a whole is not the best basis for forecasting what is going to happen on Blackfriars Bridge. Figure 2.14, copied below, shows that the number of cyclists entering Central London during the weekday morning peak rose sharply between 2007 and 2009.

In fact, the data behind the chart (.xls file here) says there was a 42% increase in cyclists entering central London between 2007 and 2009 (19,000 to 27,000). If sustained over five years this would amount to an increase of 105%, or a doubling.

We can also look at traffic counts carried out on Blackfriars Bridge itself by the Department for Transport (search for Count Point 56614 here, select 'All years', then 'Save results'). DfT counted 4,676 bikes crossing the bridge in a 12-hour period in 2007, rising to 7,395 in 2010, which is a 58% increase in three years, equivalent to a 97% increase if sustained over five years - very similar to the estimate we got from the Central London cordon counts.

So it does look as if TfL have underestimated the likely growth in cycling on Blackfriars Bridge between 2007 and 2012, by using an all-London comparator rather than the more spatially specific data available.

The localist trilemma

Prof Henry Overman of the LSE has some interesting thoughts on lessons for urban policy from Dani Rodrik's book 'The Globalization Paradox'. I'm particularly interested in Rodrik's concept of an inescapable trilemma governing world economic affairs, according to which "democracy, national sovereignty and global economic integration are mutually incompatible: we can combine any two of the three, but never have all three simultaneously and in full". Or in graphic form:

I wonder whether a similar logic applies to 'localism' and land use policy, as follows

• Strong local governments which are also very responsive to the local electorate are more likely to be NIMBYist;
• If you want to combine democratic institutions and liberal land use policy you probably need relatively weak local government, with wider interests represented by elected regional or national tiers promoting growth over local resistance;
• And if you want strong local government combined with liberal land use policy then a somewhat undemocratic 'local growth machine' is perhaps the best way to get it.

Or if you prefer the graphic version:

No doubt this is a little too neat, but I think there's something to it. Which is troubling for people who like all three things in those boxes.

The Gated City

I've just finished reading Ryan Avent's book The Gated City, which UK readers can download for Kindle or PC/Mac reading here. Anyone interested in why we've got cities in the first place, how we ended up with the ones we have, or what's going to happen to them in future should read it. In an appealingly concise ninety or so pages, you get a very clear explanation of the economic advantages of density, a compelling argument that restricting density leads to significant damage to economic growth prospects as well as social costs, and a critique of the ethics of NIMBYism which is all the more persuasive because it is so even-handed.

For a short book it raises a lot of issues, but I'm going to focus on just one or two. Firstly - and maybe this isn't a particularly fair comment on a deliberately brief tome - at some point I'd like to see a deeper exploration of why so many people have come to oppose development so much. After all, it was only as recently as the mid-1970s that Harvey Molotch was writing about how American cities were controlled by 'local growth machines', mostly driven by real estate developers, that rode roughshod over the interests of ordinary residents.

In a way, it's these growth machines that seem hard to explain now. You can see why residents wanted more control, even leaving aside some of the crimes committed in the name of urban redevelopment. It is natural to want to influence what happens to our neighbourhood, since it affects our quality of life so deeply. It is all the more natural if we are particularly attached to our neighbourhood, if it is particularly unique and attractive, or if our major asset's value is intimately tied to it (in practice, these different factors may be difficult to disentangle). Perhaps NIMBYism, like cleaner environments and longer holidays, is something that we choose to have more of as we become more affluent, even if it comes at the cost of lower overall economic growth (I say 'we', but of course as Ryan says there are real clashes of interest and distributional consequences involved).

And the thing is, falling urban densities over the course of the 20th century did seem to be accompanied by real improvements in quality of life. Present day San Francisco is an extraordinarily pleasant place. So why should those who have paid so much for the pleasure of living there have to accept it being changed, perhaps destroyed?

The Gated City is about answering that question from the perspective of society at large, and it answers it very well. But as persuasive as this rootless technocrat found it I don't think it will win over your average NIMBY in San Jose or Chelsea. So what would work? Ryan mainly suggests radically narrowing the scope of planning rules and respecting the right of people to do what they like with their property, and 'zoning budgets' so that local authorities can't restrict development in one place without freeing it up elsewhere.

I'm not sure about these. One problem with trying to radically limit the role of planning is that restrictive rules are typically extremely popular with local people, so removing them implies some sort of top-down direction that, however beneficial in the aggregate, is likely to cause a good deal of strife. Secondly, I think there is a role for planning in that there really are large potential social costs involved with development which good planning can address. There's a danger that removing the system's ability to address these externalities would just lead to more development with high social costs. The problem is that the role of planning has been left open to addressing any kind of 'impact', so people complain on purely private grounds, albeit sometimes dressed up in social terms. Perhaps I'm naive or just speaking my class interests as a sometime-planner (by the way, see the disclosure at the end of the post), but I'd like to see more of an effort to make it clearer which external costs planning can and should address and what the evidential thresholds for complaints should be before we chuck out planning altogether. As for zoning budgets, unless I'm missing something they don't seem to me to really address the legacy of existing constraints.

So what's left? I do think we could look at ways of ensuring that expensive and restrictive neighbourhoods bear more of the costs of their restrictions, which at the moment are mainly borne by others. In this country the new government has introduced a New Homes Bonus which pays local authorities for each new home completed in their area by matching the council tax income for the new home for the first six years. This will provide some additional incentive to increase supply, but the problem is that if supply increases to anything like the levels we need, much of the funding for the NHB will come from top-slicing central government grant to councils in proportion to the amount they currently receive. This means that those councils most dependent on government grant (i.e. those in deprived areas) will pay more for the NHB (if it ever takes off), unless they can get a lot of homes built themselves. In effect therefore, the strongest incentives tend to apply in the areas with lowest market demand.

I've argued that you could redesign the NHB so that it is paid for by top-slicing grant to councils in proportion to the extent of the affordability problem in each area. That would mean that the areas with highest prices relative to incomes will not just earn no NHB if they don't allow new supply, but would lose out the most in proportionate terms to those councils that are building. At the right rates this could be a sharp incentive indeed, perhaps enough to concentrate minds in some expensive areas places (this is also not a million miles from Glaeser & Gyourko's proposal of a few years back).

Now, that's obviously fairly top-down too. And anything that challenges the status quo enough to really make a change is going to be controversial and hard to implement for precisely that reason. The first step has to be to face up to the real magnitude of the costs we impose on ourselves by unduly limiting densities, and for that reason The Gated City deserves to be read very widely.

Disclosure: This post, like everything else on this blog, is informed by my work at the Greater London Authority on housing and planning policy - as a fairly minor functionary rather than someone with much decision-making power. The big decisions are naturally made by the Mayor and his advisors, taking into account a range of factors which I have the luxury of not having to deal with. Just in case it isn't clear, I'm writing in a completely personal capacity here.

Congestion and road pricing links

It's been an interesting couple of days in the wacky world of congestion and road pricing. First, the House of Commons Transport Committee tried to identify some ways to address congestion without resorting to road pricing and came up with ... not very much really, just a lot of well-meaning but essentially small-bore stuff about trying to make motorists behave better or think smarter, and the usual griping about roadworks. None of these are going to have a very big impact on congestion, as the committee probably knows. So this report is actually another piece of evidence in support of road pricing, if only by omission.

Secondly, a much less noticed but more rigorous analysis of the issue was provided by the IFS in its Mirrlees Review of Taxation, which looked at a range of issues including 'Taxes on Motoring'. They make the very important point that while the existing fuel tax regime acts as a sort of indirect tax on road use, increasing fuel efficiency has made it less and less effective in this role, which means that our only national brake on congestion gets weaker over time:

However it is done, we do not underestimate the political difficulties of introducing road pricing nationally. But in addition to the long-standing case for such a move, we need urgently to wake up to the fact that, if the UK and other countries are to meet their targets for reductions in greenhouse gas emissions, petrol and diesel use by motor vehicles is likely to have to fall and eventually end as alternative technologies are introduced. This will leave the UK with no tax at all on the very high congestion externalities created by motorists. So, if we all end up driving electric cars, it seems that we shall have no choice but to charge for road use. It will be much easier to introduce such charges while there is a quid pro quo to offer in terms of reduced fuel taxes ... Of all the challenges raised in this volume, this seems to us one that is simply inescapable. It may be another ten years before change becomes urgent, but urgent it will become and the sooner serious advances are made to move the basis of charging to one based on congestion the better.
(emphasis added)

Lastly, Dave Hill of the Guardian makes the case for the crucial role of road pricing in particular and transport policy in general in fostering urban prosperity and quality of life here.

Speak up

Matt Yglesias recommends that people who want to see progressive policy changes should (a) badger their elected representatives about it and (b) relentlessly tell their friends and family about how progressive policies would improve their lives, even if it basically involves annoying them.

If you are in a car with me and we’re in a rush hour traffic jam, you are damn well going to listen to me talk about congestion pricing. This generally doesn’t work in Washington for national politics, but whatever it is you do I’m sure you interact with lots of “apolitical” or moderately conservative people who remark now and again about things in their life to which politics is relevant. Point this out to them. Tell them who the bad guys are. Recommend some good blogs. Your friend Bob probably thinks he doesn’t care about monetary policy, but does care about the state of the labor market. Explain it to him ... These two things are, I think, the most underrated props of conservative dominance in the United States. Conservatives write and call congress at a much higher rate than progressives, and more-or-less ordinary people hear conservative political messages from preachers and business executives all the time.

That last bit is spot on. If progressives believe that many people's lives would be improved by more redistribution, better public services or (say) widespread congestion pricing, it's odd that many of them are fairly coy about saying so outright and often prefer to keep the discussion in the realm of policy wonkishness.

Perhaps it is because conservative-friendly ideas come pre-legitimised by religion, wealth or power (not to mention a supportive media), while progressive policies often (but not always) involve considerations of the common good trumping immediate self-interest. Maybe that's a harder sell, but that's just all the more reason to put the effort into selling it.

I agree with Matt that road pricing / congestion is a case in point. The example of London shows that it would lead to improvements in quality of life and free up space to provide for buses, pedestrians and cyclists. The benefits would also overwhelmingly flow from the better off to the less well off. Yet hardly anyone seems willing to publicly advocate it. I guess they may be scarred by the experience of the lost Manchester referendum, but then that's a reason to be out there organising support and building coalitions so that the next time around there is a stronger strategy with a stronger chance of winning. In other words, don't be shy about your convictions, because you can be damn sure the other side won't be.