the ubiquitous blog

As readers of this blog will know I regard the introduction of 20mph speed limits as a good thing, and as I have said elsewhere, it has been known for well over 20 years that, as traffic speed increases, so does the risk to pedestrians:

• Hit by a car at 20 mph, 3% of pedestrians will be killed – 97% will survive
• Hit by a car at 30 mph, 20% of pedestrians will be killed – 80% will survive
• Hit by a car at 35 mph, 50% of pedestrians will be killed – 50% will survive
• Hit by a car at 40 mph, 90% of pedestrians will be killed – 10% will survive
• Hit by a car at 50 mph, >99% of pedestrians will be killed – < 1% will survive

Many drivers don’t think about the fact that at 30 mph, a vehicle travels 44ft (roughly three car lengths) every second and at 20mph a vehicle travels 29.3ft (roughly two car lengths). The average reaction time of drivers is between 1 and 1.5 seconds, it takes time to stop, drivers have to think ahead rather than just trying to react to the situation. Lowering the speed limit allows driver more time to think and therefore reduces the frequency of accidents collisions.

However, if a 20mph speed limit is to be effective it has to be enforced, so I was very disappointed be the following twitter correspondence:

@DrCarolineBrown #askLBP However, traffic support wardens carry out regular speed checks at schools, advising motorists of 20mph limits.

— LBPolice(@LBP_Police) June 19, 2012

@kim_harding you are right LBP said #20mph are not enforced but controlled with chicanes and speedbumps #edinburgh #cycling.

— Caroline Brown (@DrCarolineBrown) June 19, 2012

@LBP_Police no chicanes or speed bumps in my street; just (small) signs #20mph #edinburgh #cycling

— Caroline Brown (@DrCarolineBrown) June 19, 2012

@kim_harding seems like it, with enforcement only at/near schools!

— Caroline Brown (@DrCarolineBrown) June 19, 2012

which leads to the question what are 20mph speed limit for? Or for that matter what are the police for, if they lack any real interest in community safety? Clearly the police aren’t interested in saving lives by enforcing speed limits, which may go some way to explain why the rate of pedestrians being killed or serious injury on our roads is currently increasing. This will continue to increase until driver change their behaviour and realise that they have a responsibility to drive below the speed limits and stop killing people.

The news has come through that the proposed 20 mph speed limit zone in South Edinburgh has been given the go ahead, which is good news. However, it is rather disappointing that the most dangerous roads inwith the area covered by the zone are being left at the higher 30 mph speed limit. As I have said elsewhere, it has been known for well over 20 years that, as traffic speed increases, so does the risk to pedestrians:

• Hit by a car at 20 mph, 3% of pedestrians will be killed – 97% will survive
• Hit by a car at 30 mph, 20% of pedestrians will be killed – 80% will survive
• Hit by a car at 35 mph, 50% of pedestrians will be killed – 50% will survive
• Hit by a car at 40 mph, 90% of pedestrians will be killed – 10% will survive
• Hit by a car at 50 mph, >99% of pedestrians will be killed – < 1% will survive

Many drivers don’t think about the fact that at 30 mph, a vehicle travels 44ft (roughly three car lengths) every second and at 20mph a vehicle travels 29.3ft (roughly two car lengths). The average reaction time of drivers is between 1 and 1.5 seconds, it takes time to stop, drivers have to think ahead rather than just trying to react to the situation. Lowering the speed limit allows driver more time to thing and so reduces the frequency of accidents collisions.

It is also well known that the majority of drivers think that it is OK to exceed any given speed limit by 5-10 mph. As you can see from the bullet points above, this greatly increases the risk to pedestrians. However, there are some people and organisations who don’t seem to care about this, rather worryingly these include the Lothian and Borders Police, and Lothian Buses. It is widely felt that the grounds for objection were rather thin.

The Police claim they would need extra resources to enforce the lower limit if the major routes were included, and yet these are the routes which are currently in need of the greatest enforcement. If the limits on these roads were to have regular speed traps, the accident crash rates could be significantly reduced. This would in turn save the police money, as they would use fewer resources dealing with the aftermath of these crashes. Lothian Buses claim that the speed reduction on main routes would delay services and therefore require them to provide additional buses at extra cost. However, there is no evidence from other cities which have introduced 20 mph speed limits to support this. The evidence is that lower speed limits tend to smooth traffic flows and reduce the effect of congestion on bus services.

There were even objections on environmental grounds, with the Council Air Quality Monitoring Unit having concerns about the introduction of the 20mph speed limit on the busier bus corridors, due to higher gear ratios at lower running speeds resulting in greater tailpipe emissions. They claim that this is true for all vehicles, with slower buses and HGVs likely to contribute more to air quality issues in the city. Again, the evidence for this appears rather thin, this could easily be dealt with by encouraging drivers to use (appropriate) lower gears. In fact, in previous trials in cities like London and Portsmounth the introduction of 20 mph zones resulted in improved air quality. So this is really more of an excuse for not grasping the nettle and actually reducing motorised traffic through the city. The Council has a history of doing this and there have been issues with its air quality monitoring in the past.

These objections fly in the face of wide spread support from a large number of people living inwith the zone and the community councils which represent them, who had actively lobbied for the number of roads covered by the 20 mph speed limit to be increased. While the introduction of the zone is to be welcomed, it is in many ways an opportunity missed. As Councillor Steve Burgess, put it: “I was disappointed with the decision. We missed the opportunity to do something quite bold that maybe puts pedestrians and cyclists on a safer footing with vehicles in the area. It would have been good to do the whole scheme and include those roads in the pilot at the same time. I don’t think the claims by Lothian Buses and the police hold much water. It’s a missed opportunity, especially considering the community councils were supportive.”

The full report from the meeting of the Council’s Transport, Infrastructure and Environment Committee can be downloaded here

The City of Edinburgh is currently in the possess of introducing a 20mph speed limit across a large area of the south side of the town. This is something which I am very much in favour of as it will make the city a safer and more pleasant place to live. The one thing I don’t really understand is why the most dangerous roads inwith the proposed zone are being left at the 30mph speed limit. Some of the roads which were originally going to be left with a 30mph limit are now proposed to have their speed limits reduced due to community pressure during the conciliation process. However, not all, I have to cross some of these roads everyday, there is a primary school which is bounded on two sides by roads which are being left at 30mph! Why not all the roads in the zone? Well it would appear that there are those who are objecting to any reduction in the speed limits. Well, my attitudes to anti speed limit campaigners can be expressed by substituting “speed limit” for “speed bump” in this video clip from episode six of Outnumbered, season 3.

I hope that makes things clear…

Addendum: It turns out that the two biggest objectors to the introduction of the 20mph speed limit are Lothian Buses and Lothian & Borders Police!

As regular readers will know, I am keen to see traffic laws to make the roads safer for all. When I heard that the City of Edinburgh Council was proposing to introduce a 20mph speed limit across a large area of South Central Edinburgh, I though this was a great idea and one for which Councillor Gordon Mackenzie (Convener of the Transport, Infrastructure and Environment Committee) should be commended. The proposed scheme is currently going through the consultation phase, with all households in the area covered by the scheme being sent a leaflet, I received mine today.

The Council leaflet explains that “lower speeds make people feel safer when they are walking and cycling and make streets better places to live”. This is widely known outwith the UK, many countries in Europe have 30Km/h (18.6mph) speed limits in built up areas. So there is a wealth of data on the effects of these lower speed limits, not only do they feel safer, they are safer. Barcelona, for instance, showed a 27% drop in accidents in one area of the city after bringing in a 30Km/h speed limit. One study in London showed that the introduction of 20 mph zones was associated with a 41.9% reduction in road casualties. The same study showed the greatest percentage reduction was for younger children and greater for the category of killed or seriously injured casualties than for minor injuries.

It has been known for well over 20 years that, as traffic speed increases, so does the risk to pedestrians:

• Hit by a car at 20 mph, 3% of pedestrians will be killed – 97% will survive
• Hit by a car at 30 mph, 20% of pedestrians will be killed – 80% will survive
• Hit by a car at 35 mph, 50% of pedestrians will be killed – 50% will survive
• Hit by a car at 40 mph, 90% of pedestrians will be killed – 10% will survive
• Hit by a car at 50 mph, >99% of pedestrians will be killed – < 1% will survive

Many drivers don’t think about the fact that at 30 mph, a vehicle travels 44ft (roughly three car lengths) every second and at 20mph a vehicle travels 29ft (roughly two car lengths). The average reaction time of drivers is between 1 and 1.5 seconds, it takes time to stop, drivers have to think ahead rather than just trying to react to the situation. Lowering the speed limit allows driver more time to thing and so reduces the frequency of accidents collisions.

There are also other benefits to having a lower speed limit: Reducing the speed limit from 30mph to 20mph reduces noise by 3 decibels. Not only is traffic noise annoying, it damages people’s health by disturbing sleep, causing cardiovascular and psycho-physiological effects. Lowering the speed limit from 50 km/h to 30 km/h has been shown to reduce emissions CO₂ (about 15%), NO_x (about 40%) and CO (about 45%). Also, a lower speed limit can help traffic to flow more smoothly, but only if drivers change their behaviour.

So there is much to welcome in this proposal. However, on looking a little closer, I saw that this isn’t the blanket 20 mph speed limit that I was expecting. No, there are nine “arterial routes” that are being left at 30mph, which really blows a hole in the whole thing. It is known that isolated schemes endorse driving faster outside of the zone, so the current proposal will have the effect of increasing speeds on the “arterial routes”, is this really a good idea? If you take a map of Edinburgh, lay a clear sheet over it, plot the locations of the accidents crashes over the last few years, take away the map, and what do you see?

The image above is taken from the Traffic Injury Map.

The outline of the “arterial routes” which are being left out of the 20 mph zone! If this proposal isn’t changed, it will fail to achieve its full potential, surely the roads which need the lower speed limits most are the ones with the highest accident rates, otherwise what is the point? Don’t the people living along the “arterial routes” deserve a better quality of life, too? So if a 20 mph speed limit is good for the residents of Kirkhill Road, why not for those living in the tenements of Dalkeith Road? Or why should people living in Millerfield Place have greater protection that people living along Marchmont Road? Surely these improvements in quality of life should be for all those living inwith the 20 mph zone.

If you agree that this proposal flawed (or even if you don’t), you can give your feed back here.