The Sun, 20 mph speed limits, and a lot of nonsense

CONTROVERSIAL 20mph speed limits designed to cut road casualties are not working, official figures show.

So says The Sun anyway*. So, what’s the problem?

A report from the Department for Transport shows there were 2,262 fatalities and injuries in 2011 on 20mph roads in built-up areas — 24 per cent more than in 2010 when 1,827 were recorded.

That compares to a one per cent reduction in casualties on 30mph roads in built-up areas.

How many people died or were injured on roads with a 30 mph speed limit then? The Sun doesn’t say, but the official data is easy enough to find. In 2010, 127,377 people were killed or injured on a road with a 30 mph speed limit. In 2011, it was 125,494.

In other words, that “1% drop” corresponds to almost 2000 fewer people were injured on 30 mph roads, while 400 more people were injured on 20 mph roads. That is a net decrease of 1448 injuries/deaths.

Just looking at the number of injuries on 20 mph roads is not going to tell you about how effective 20 mph speed limits are. You have to compare them with other speed limits. Data about how many 20 mph zones there are is hard to find, which makes making sense of the Sun‘s data difficult, but it certainly looks like a lot of them have been springing up lately, so an increase in injuries is to be expected – if there are more roads, there will always be more accidents!

Studies of 20 mph zones consistently find that the same stretch of road will see fewer accidents and fewer injuries if the speed limit decreases from 30 mph to 20 mph, especially if this decrease is enforced by speed bumps and other traffic calming measures.

* Incidentally, far from being “controversial”, surveys consistently find around 74% in favour of 20 mph speed limits and just 12% against them.

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Will driving at 80 mph help the economy? Statistics say… probably not

Last week, the Transport Secretary Phillip Hammond announced plans to raise the speed limits on motorways from 70 mph to 80 mph. This, he claimed, would:

“generate economic benefits of hundreds of millions of pounds through shorter journey times.”

Never mind the debates about safety and the environment, let’s look at this one argument. So, does a shorter journey equal a more economic journey? The problem is that cars need more fuel to travel faster, and so the faster you go, the worse your fuel efficiency is. Statistics that go right up to 80 mph are hard to find for some reason – the big US government study for example only went up to 75 mph – but according to the calculator at MPG for speed (better sources always appreciated), driving at 80 mph uses about 15% more fuel per mile than driving at 70 mph.

So, lets do some maths! For the sake of simplicity, we’ll assume every single journey on the motorways is work-related. The actual figures will be lower, especially on weekends and holidays.

At 70 mph, it takes 51 seconds to drive 1 mile. In this time, a car with a claimed “highway” fuel efficiency of 40 miles per gallon (roughly as efficient as a modern hatchback like a Ford Fiesta) will use about 0.11 litres of petrol. At the current average pump price, that’s 15 pence of petrol.

At 80 mph, you cover that same mile in 45 seconds, saving you 6 seconds. On the other hand, your car is now 15% less efficient. According to the calculator, your 40 MPG car is now doing just 28.8 MPG, using around 0.13 litres of petrol to cover that mile, so the fuel to travel that distance cost you about 18 pence.

Spending 3 pence to save 6 seconds is equivalent to spending £18 to save 1 hour. The average median wage in the UK is far lower than £18 an hour (currently, it’s £12.50 per hour for full-time workers (PDF))* – in other words, if you drove at the speed limit to get to/from work, the money you’d be spending on petrol would mean most people would actually lose out (people who car-share would be in a better position, but few people car-share to work).

All the extra pay taken home by workers would simply end up going straight to the petrol companies – and when the government is trying to increase consumer spending, that’s the last thing the economy needs.

(Oops, forgot to mention that this post bears a debt of inspiration to this xkcd comic.)

* Thanks to Lukeablancas in the comments for pointing out that I’ve gone for the median wage. The median wage is good for working out what this means for the average person, since it’s unaffected by extremes, but if we’re looking at the country as a whole, the mean wage might be better – this will take high-earners like company bosses into account, as well as people who work in short but intense shifts, like some freelancers. In 2010, the mean wage for men was £16.00 per hour and for women it was £12.92 per hour (annoyingly the government hasn’t released the combined figures for men and women, but assuming there are roughly equal numbers of both in work the average wage overall is £14.46 per hour). Either way, on average people will end up losing out.

Car crash journalism

That damn war on motorists, eh? Not only did they put a bus lane on the M4 (which actually improved traffic flow significantly), now they’re putting 20 mph speed limits on roads! Naturally, the Daily Mail is unhappy, and now they have the ammunition to take these speed limits down! M… maybe.

Why death rates INCREASED in 20mph zones… and getting rid of cameras reduces accidents says today’s Mail. Now, you might think that with the headline beginning with the word “why”, that mean the Daily Mail was going to tell us why death rates increased. Of course, they don’t. That might be because death rates didn’t really increase at all in any meaningful sense.

“Insane bus lane” not insane

It doesn’t take much to get the papers riled up, and the first mention of the ridiculous phrase “war on motorists” gets the predictable Pavlovian response from the papers all racing to defend the common man (or at least Jeremy Clarkson): The Telegraph runs with “Prescott’s M4 bus lane to be scrapped“, The Daily Mail with “End of the road for Prescott’s M4 bus lane as Tories scrap ‘symbol of Labour’s war on motorist’” and The Sun goes for “Tories to ditch insane bus lane“.

All of these articles try their hardest to give the impression that the M4 bus lane didn’t work, with photographs of empty bus lanes next to huge traffic jams. The bus lane is called “controversial”, “insane” and a “folly”. There could be no doubt that it didn’t work. Except…

What none of them mention is that the M4 bus lane reduces journey times – not just for buses and taxis, but for regular vehicles too. Thanks to the bus lane, drivers can now travel between junction 3 and junction 2 up to 6 minutes faster.

You see, the M4 bus lane doesn’t just let traffic get around the jams. It also stops a nasty bottleneck forming when the three lane motorway has to cross a two lane viaduct (which was in all likelihood the main reason for the bus lane being built). If the M4 bus lane gets reopened to cars, all that will happen is that that bottleneck will return and traffic jams will worsen.

If there’s anyone who’s declared “war on motorists”, surely its the politicians and journalists who want to increase congestion and deliberately complicate the road layout just to score a few political points?

EU does something involving motorists, Daily Express explodes

Perhaps I should just rename this blog “Lies the Daily Express tells every damn day about the EU” and be done with it.

“Now EU plans to make our roads pay as you go” they tell us today, which is a shame because you get unlimited internet access and 500 free minutes on contract.

MOTORISTS could be squeezed for millions in crippling toll charges if EU chiefs seize control of Britain’s roads and motorways.

European Commission bureaucrats are plotting to merge the UK’s main traffic routes with those on the Continent to form a transport network under their control.

The EC has already agreed to launch the European Electronic Toll Service (EETS) on all current the stretch of M4 over the Severn Bridge.

Sounds like a bad prequel to some dystopian postcyberpunk epic.

In actual fact, of course, the EU does not plan to become the Darth Vaders of the road network. All they want to do is upgrade the computer systems on the Severn Bridge so they’re compatible with toll collection systems across the EU, making things slightly easier for haulage firms who carry things across the Channel.