Another HGV death in London (split from original thread)

[PK99]

[QUOTE 2781094, member: 45"]Well that will be why he wrote "about the same" rather than using the figures then. Using your stats-

Amsterdam 1 death per 83333 trips
London 1 death per 42857 trips

That's 1.94x more deaths in London per journey. I'd say it's virtually twice. Where's the parity in that? If you're discounting whole-country statistics then your journey distance statistic is irrelevant.[/quote]

Trip numbers is not a particularly useful stat if trip length is very different

Moreover, deriving from the Wikipedia article on cycling in the Netherlands, the average journey distance is only 4km (2.5 miles). I can't find stats for London, but I'd be amazed if it wasn't much longer - the typical cyclist in London is a cross-city or a suburb-to-city ride

From my observation of cycling in Holland, Belgium and Lille by far the vast majority of cyclists there are on sit up and beg bikes and pootle at pretty low speed.
Contrast that with many of the cyclists in central London, riding fast on fast road bikes, choosing to weave in and out of traffic.

It would be useful to have a breakdown in the London stats: who is it that is involved in most KSI's?
The experienced cyclist putting in many miles or the pootler doing fewer lower speed miles.

 

[srw]

You are asking a lot of the stats compilers there

Quite. The numbers are so low that people don't tend to bother. They're also incredibly difficult to define, and don't actually tell you a great deal.

I did wonder when someone would get on to the KSI thing. I think that's another statistical red herring. For a start, there's no standard international definition of Seriously Injured, so no international comparability. Then there's the fact that SI is a matter of judgement, not fact. Then there's the fact that the KSI numbers are broadly stable when measured relative to the number of cyclists.

Then there's the fact that "seriously injured" in statistical terms doesn't actually mean what you might expect - and it certainly doesn't mean "not killed but for a quirk of fate". Here's what it does mean in the UK:

The UK definition covers injury resulting in a person being detained in hospital as an in-patient, in addition all injuries causing: fractures, concussion, internal injuries, crushings, burns (excluding friction burns), severe cuts, severe general shock which require medical treatment even if this does not result in a stay in hospital as an in-patient.[2]

My perception is that most reports on this forum (and there are an awful lot) of serious injuries according to this definition are self-inflicted - people falling off because they're going too fast downhill and breaking a bone. This is borne out by a quick google search, unearthing this quote from a bit of helmet research (OK, American not British):

The most common cause of crashes was loss of control by cyclists causing the cyclist to fall to the ground or hit an obstacle. Motor vehicles were involved in only 15 percent of crashes

And, to round it all off, I blame the Tories. Seriously. Over the last few years A&E funding has not kept up with demand. That means that more people are being admitted as inpatients because they can't be treated in A&E within the four-hour target time. Each one of those (and Mrs W was one a couple of years ago) is automatically counted as a "serious injury" even if (as in Mrs W's case) the injury is something that will heal of its own accord within a couple of weeks.

 

[deptfordmarmoset]

And, to round it all off, I blame the Tories. Seriously. Over the last few years A&E funding has not kept up with demand. That means that more people are being admitted as inpatients because they can't be treated in A&E within the four-hour target time. Each one of those (and Mrs W was one a couple of years ago) is automatically counted as a "serious injury" even if (as in Mrs W's case) the injury is something that will heal of its own accord within a couple of weeks.

In respect of the final point up there Î I was wondering, when I saw the deteriorating KSI statistics v the K alone stats confrontation during this week's Mayor's Questions (Jenny Jones v BJ, notably), whether improvements in emergency surgery (alongside an increase in KSI injuries per trip over a 10 year period) were working to make cycling less fatal as it becomes actually more dangerous per journey. JJ was quoting TfL's actual figures on KSIs and her point was that, while fatalities were lower, you could do fewer journeys (over 400,000 10 years ago, now in the 360,000s) without becoming a KSI statistic.

Admittedly, the definition of SI may have changed in that period, but as BJ and ally Andrew Boff referred to JJ as hysterical or a scaremongerer rather than saying that she'd failed to take into account a change in the way the SIs were defined accounted for the deterioration suggests that personal insults were the only way they saw of moving onwards without change.

 

[srw]

One more thing to add to the mix. There's a House of Commons report on road safety which very clearly shows that A roads are more dangerous than other roads. You're more likely to end up a KSI statistic if you ride on them - by a factor of 3 or 4. What I can't find is a stat telling me whether the distance people have cycled on A roads has gone up - but that's certainly my suspicion.

If I've got one message to get across in all this statistical barrage it's that the statistics are sketchy and shaky. Just because you believe you've spotted something it doesn't mean that you have - unless it's that cycling is statistically far safer than you'd believe looking at the road warriors in london.

 

[PK99]

If I've got one message to get across in all this statistical barrage it's that the statistics are sketchy and shaky. Just because you believe you've spotted something it doesn't mean that you have - unless it's that cycling is statistically far safer than you'd believe looking at the road warriors in london.

well said!

 

[srw]

How funding is spent by hospitals is decided by the trusts - not by government. Good trusts have ensured that sufficient funding is given to A&E.

Fair enough - but everything you say reinforces my point that a rise in the KSI stats doesn't necessarily mean the roads are getting worse.

For the sake of completeness, here's a relatively short list of reasons why a 10% increase in KSI per billion km might not be bad news for cyclists:

• Hospitals may be recording "SI" where they didn't previously.
• Hospitals may be getting better at recording that a patient is a cyclist.
• Cyclists may be cycling more on A roads which are more dangerous.
  
• Cyclists may be doing less road riding and more mountain biking, where the risks are higher.
• More cyclists may be taking part in group riding, e.g sportives, without recognising the increased risk this brings.
  
• Cyclists may be taking more risks, perhaps because they may generally be becoming less experienced (don't forget that very many incidents - probably the large majority - are cyclist only or cyclist-on-cyclist).
• The recorded distances that cyclists ride may be understated because the methodology is flawed. This may be because it uses traffic counts on main roads only, so undercounts lane and off-road riding.

I could probably keep going all day on that list, but I'll stop there. All of the above are easily supportable by anecdote. Some may be supportable by statistics too. In particular, the people at National Statistics who compile the KSI stats themselves acknowledge the last - to the extent that they are reviewing their methodology because the traffic count stats contradict what cyclists themselves say.

 

[srw]

[QUOTE 2781094, member: 45"]
That's 1.94x more deaths in London per journey. I'd say it's virtually twice. Where's the parity in that? If you're discounting whole-country statistics then your journey distance statistic is irrelevant.[/quote]
I think it's worth exploring this a bit more.

First - the journey distance statistic isn't irrelevant. It's a standard way of comparing road risk.
Second - you've cited your multiple to 2 decimal places. I'd be wary of citing even one significant figure.

Here are some statistics that are pretty reliable - the exact number is somewhere within about 5% of the statistic. These are statistics that are easy to measure in that the definitions are clear and, in the case of population, the statistic has very many uses.

• There are about 6 cyclist deaths per year in Amsterdam and 14 in London.
• The population of London is about 8 million and the population of Amsterdam is about 800,000.

Here are some statistics that are moderately reliable - the exact number is probably within 25% of the statistic, if it exists. These are statistics that are more difficult to measure and not desperately interesting except for one particular use.

• Amsterdam and London have about the same number of cycling trips per day.
• A higher proportion of the population of Amsterdam cycle than that of London.
• Londoners probably typically take longer trips by bike than Amsterdammers.

And here are some reasons why we need to be incredibly careful comparing Amsterdam stats with London stats:

• London is a major international city; Amsterdam is a small regional centre.
• Both London and Amsterdam are cities which attract people from their regions for work, and therefore many of their cyclists are not locals.

Finally, here are some measures which speak of different things.

• Per head of population, London has fewer cycling deaths than Amsterdam, and fewer cycling deaths than pedestrian deaths or murders or deaths from heart disease. This will be the key stat for government, as it will inform the distribution of resources towards reducing death.
• Per journey, London probably has somewhat higher cycling death rates than Amsterdam. This is probably not very interesting, as it has a huge number of confounding variables and is based on a tiny sample size.
• Of those cycling deaths in London, a disproportionate number are caused by HGVs and buses. This is hugely important, as it speaks to some very simple interventions which could significantly reduce cyclist death - if that is a desired outcome of public health policy.*
  
• Per billion km cycled, London is probably a similarly safe city to Amsterdam - although the exact comparators are not very clear. This is also important, as it tells us that the solution of Amsterdam - mass cycling and mass segregation - is not necessarily the only way to make a city safe for cyclists.

In this whole debate I'm reminded of the global warming debates. There's an awful lot of froth from people who haven't understood that the story isn't as simple as it might appear from a cursory glance at some statistics.



*For the avoidance of doubt, I think it is - but others probably disagree.

 

[deptfordmarmoset]

When it comes to the deterioration in TfL figures we could presumably discount mountains (except anecdotally, of course) and sportives (there may be some but I doubt that there are many in the Greater London Area). And we could take into account that during rush hour periods cyclists make up 24% of road traffic in central London. That's where the cyclists are at least at one point of the day so we have a good idea about where the KSI figures are most probably coming from.

 

[srw]

When it comes to the deterioration in TfL figures we could presumably discount mountains (except anecdotally, of course) and sportives (there may be some but I doubt that there are many in the Greater London Area). And we could take into account that during rush hour periods cyclists make up 24% of road traffic in central London. That's where the cyclists are at least at one point of the day so we have a good idea about where the KSI figures are most probably coming from.

Agreed about mountains and sportives in the specific case of London (which, fair enough, is what this thread's about). But the increase in number of seriously injured over one year is 100 - which could quite easily be random variation. Indeed, the TFL report points out that the change wasn't statistically significant.

I'd take that 24% stat with a pinch of salt myself - it means that it's somewhere between about 20% and 30%, and it only refers to central London, not Greater London. My suspicion is that outer London is seeing as much growth in cyclist numbers as central London, but doesn't seem to have the same increase in casualties.

 

[RedRider]

I posted this elsewhere but it's highly relevant to this thread. Chris Boardman speaks out on the relative risks of cycling, wearing helmets and hi-viz and where responsability lies. He was speaking during the media furore after Wiggins was hit by a car when out training (two years ago?)
To my mind he's the most reasoned and respectable high-profile voice in cycling advocacy. (I guess I would say that because I agree with him just about entirely.) He's interviewed from 2.15 onwards and if you're not cheering or at least nodding your head vigourously by the end then I don't know what. Be interesting to hear people's views on on what he says and him as a cycling advocate. Well worth a watch but I recommend starting at 2.15.

There's also a link to a recent interview with Chris in the thread about Hogan-Howe's comments re cycling in London.

 

[albion]

You will probably find that certain danger spots in London are maybe 10,000 times above the usual safe risk level.

Risk per trip are thousands of times greater on some journeys compared to others.

 

[deptfordmarmoset]

Agreed about mountains and sportives in the specific case of London (which, fair enough, is what this thread's about). But the increase in number of seriously injured over one year is 100 - which could quite easily be random variation. Indeed, the TFL report points out that the change wasn't statistically significant.

I'd take that 24% stat with a pinch of salt myself - it means that it's somewhere between about 20% and 30%, and it only refers to central London, not Greater London. My suspicion is that outer London is seeing as much growth in cyclist numbers as central London, but doesn't seem to have the same increase in casualties.

I'm not a statistician but TfL have specifically targeted the outlying areas for development because their figures suggest that the increase in modal share is stubbornly poor. It's figures again, of course, but at least they're TfL figures, and they appear to have been sufficiently convincing for TfL to push what is effectively a catch up program. The dominance of arterial corridors in the suburbs and a lack of alternative routes may be largely down to the slower development. Bow roundabout would be a notorious example of this: everything heading west into town, north and south (Blackwall tunnel in the South East to the M11 in the North East) is channelled over the River Lea at one point.

 

[srw]

The dominance of arterial corridors in the suburbs and a lack of alternative routes may be largely down to the slower development.

Or it may be because in the suburbs the arterial routes are the most attractive!

Certainly my favourite way into London from home is the A404. Most of its junctions are fine - the exception is the rather awkwardly laid out Northwick Park roundabout. When I took the alternative route (the LCC's back route) I found myself going downhill at 20mph on what was effectively a single-track road taking two directions of traffic, because of the parked cars. And I found myself traversing the North Circular on a motorway-style underpass roundabout.

I suspect that the simplest way to improve cyclist safety in London is first of all to sort out the HGVs (easy - there are already so many controls over London traffic that one more won't make a difference) and then sort out the main road junctions (fairly easy - strip out the roundabouts, and control everything with traffic lights with proper advanced bike phases). Incidentally, both will also make being a pedestrian far safer and more pleasant.

 

[deptfordmarmoset]

Or it may be because in the suburbs the arterial routes are the most attractive!

Certainly my favourite way into London from home is the A404. Most of its junctions are fine - the exception is the rather awkwardly laid out Northwick Park roundabout. When I took the alternative route (the LCC's back route) I found myself going downhill at 20mph on what was effectively a single-track road taking two directions of traffic, because of the parked cars. And I found myself traversing the North Circular on a motorway-style underpass roundabout.

I suspect that the simplest way to improve cyclist safety in London is first of all to sort out the HGVs (easy - there are already so many controls over London traffic that one more won't make a difference) and then sort out the main road junctions (fairly easy - strip out the roundabouts, and control everything with traffic lights with proper advanced bike phases). Incidentally, both will also make being a pedestrian far safer and more pleasant.

Yes, when the alternative routes are so poor, so meandering, and so often clogged up with carlesterol, arterials (ideally with bus lanes) are more attractive, despite the increased number of traffic lights.

I'd agree that sorting out the HGVs would be easy in principle, the snag is that nobody yet is prepared to own the responsibility for doing so, Boris least of all.

 

[RedRider]

carlesterol

I'll nick that.