Entries tagged with “20mph speed limit”.


For 6,000 years the street was a place where people met and talked, they traded and did business, above all they could walk where they liked. The street was a democratic space which belonged to no one group or form of transport. This all ended in the 20th Century with the arrival of the motorists who demanded that they had a greater “right” to use the road than anyone else. Pedestrians were forced to the sides and restricted in where they could cross, cyclists were barely tolerated and expected to keep out of the way. How did all this come about?

When the car first arrived, they were few in number and tightly controlled as it was recognised that motor vehicles were a danger to all. However, as the people who owned cars were wealthy and powerful these measures were soon being watered down. First off, the 1865 “Red Flag Act” was replaced by the Highways Act 1896 which set a limit of speed limit to 14mph (23km/h). This change is still commemorated each year by the London to Brighton Veteran Car Run. Then in turn this speed limit was replaced by the Motor Car Act 1903, which raised the limit again, this time to 20mph (32km/h), which is where the speed limit in built up areas should have stayed.

However, after a great deal of pressure from the motoring lobby, all speed limits for cars and motorbikes were removed by the Road Traffic Act 1930. It is very telling that Lord Buckmaster’s opinion at the time was that the speed limit was removed because “the existing speed limit was so universally disobeyed that its maintenance brought the law into contempt”. It is also worth noting that the AA was founded in 1905 to help motorists avoid police speed traps, and the RAC also has a long history of lobbying against speed restrictions.

At this time there were relatively few cars on the roads but the death rate was considerable. Data on road deaths in Great Britain were first collected in 1926, in that year there were 4,886 recorded deaths. The result of the removal of all speed limits for cars meant that in 1931 the death rate hit a new high of 7,343 deaths and 231,603 serious injuries. As a consequence, the new Minister of Transport, Leslie Hore-Belisha, described it as “mass murder” and reintroduced a speed limit for cars at 30 mph in built-up areas (defined in Scotland as areas where the lighting columns are spaced at 185m or less).

But is 30mph an appropriate speed for motor vehicles in a built up area? Well no, as this infographic from Pedal on Parliament [http://pedalonparliament.org] clearly shows:

Speed & Fatalities

As speed increases so the survivability of a collision declines. Why would this be?

It’s a simple matter of physics, if streets have large amounts of kinetic (movement) energy moving along them they are more hazardous places to be. Kinetic energy can be shown by the equation Ek = 1/2mv2, where Ek is the amount of kinetic energy (usually given in Joules), m is mass or weight of the vehicle (usually given in Kg), and v2 is velocity or speed which is squared (usually given in meters per second). But what does this mean in reality? Let’s look at the kinetic energy of a small car, these weigh about one tonne (1,000Kg) travelling at 20mph (8.9m/s), so Ek = 0.5 x 1,000 x 8.92 = 39,969J (39.97kJ).

This also tells us that as speed increases, because velocity is squared, the amount of energy increases exponentially. If the vehicle speed doubles, then its kinetic energy quadruples, so at 40mph a one tonne car will now have a kinetic energy of 159.88 kJ. It also tells us that heavier cars are more lethal than lighter ones, so a big 4×4 which can weigh about three tonnes, will have a kinetic energy of 119.91kJ at 20mph and 479.63kJ at 40mph. Just to put all this into context, the kinetic/muzzle energy of a 12 bore shotgun is 4.45kJ. OK so there are some differences is the area over which the kinetic energy would be transferred, but it shows just how lethal cars can be.

Before I move on, just a quick note on the data source for the infographic above. When Donald was drawing it up, we at PoP had a discussion about which paper to take the data from and why. There are a couple of newer papers which appear to give higher survival rates at 30 mph. However, when you read the original source material, you find that the most vulnerable groups, children under 15 years and adults over 70 years, have been excluded from the analysis. No reason is given for this exclusion of data and the reader is left to draw their own conclusions, so we chose to use Aston & McKay 1979. We have received a certain amount of criticism for using “old” data, but as I have shown above, the laws of physics haven’t changed. People say that cars have changed, and yes they have, they have gotten bigger and heavier. A small car in 1979 would have weighed 500-750Kg, now 1,000 Kg, and there were very few 4×4 SUVs. The levels of kinetic energy on our roads for the same speeds are greater than they were before.

Of course the level of kinetic energy is not the only factor that makes lower speed limits safer in built up areas. There are other things to think about too, such as stopping distances, here again the same laws of physics come into play. There is the relationship between driving speed and braking distance. The kinetic energy of a vehicle is proportional to the square of its increased speed, this means that as the driving speed is doubled the braking distance quadruples. Of course there will be those who say the brakes on modern vehicles are better than they used to be. But they are not (as some drivers imagine them to be) magic, they can not overcome the laws of physics. Anti-lock brakes do not significantly reduce braking distance on a dry road, they merely reduce the risk of skidding out of control. Of course braking distance is only one component of Stopping Distance, the other part is thinking distance.

The speed with which the human brain can think hasn’t changed in well over 3 million years, no matter how much some people might want to think otherwise. (Insert your own joke here about Neanderthal taxi drivers). For an alert driver the average time between seeing a hazard and applying the brakes is 1.5 seconds. This means that at 20mph (32Km/h) the driver travels 13m while still thinking, this compares with 20m at 30mph (48Km/h) and 27m at 40mph (64Km/h). Remember this is for an alert driver, increasingly drivers are increasingly distracted by things like mobile phones and satnav systems. This can be the difference between life and death for a pedestrian or a cyclist using the same road.

As speed rises so the amount of time the driver has available to look around for hazards reduces and so does their peripheral vision.

peripheral vision image

In a busy environment there is a need for the driver to be more aware of what is going on around them. In less busy environments, i.e. motorways where the traffic is all moving in the same direction and there are fewer hazards coming from the sides, allowing the driver to focus more on what is happening in the distance. This is why motorways are generally considered to be safer than urban roads, even though motorways have higher speeds. As any trained advanced driver can tell you, driving at any speed requires constant attention and observation.

Aside from the clear safety benefits of 20mph speed limits for all road users, there are also other benefits to keeping the speed of motor vehicles below 20mph in built up areas. These include reductions in air pollution and noise pollution, both of which have an impact of human health.

There is increasing evidence that air pollution is shortening all our lives. Reducing motor vehicle speeds reduces levels of air pollution at source, so this has to be a good thing. There are some who claim that there are modelling studies suggesting that 20mph speed limits would increase pollution levels. However, there are no measurement studies I can find that bear this out. Models are only as good as the data and assumptions on which they are based, if they can’t be validated by real world data, they are worthless.

By reducing speeds by 10mph, traffic noise is reduced by about 3dB (depending on road surface). High levels of traffic noise cause stress and discourage active travel – who wants to walk along a noisy urban street? This not only bad for the health of people living in urban areas (and the majority of people do now live in urban areas), it is also bad for the local economy as it makes local shopping less attractive. “High street” businesses rely on footfall, not drive past. A study in the UK showed that people who walked to town centres spent an average of £91 per week on shopping, while motorists would spent £64 per week. Edinburgh’s bold move to bring in an almost blanket 20mph speed limit (excluding major roads), will help to make the whole city more vibrant.

The introduction of the 20mph speed limit in Edinburgh has been a long process, first we had the Southside trial. Then there was a two year consultation which showed there is significant support for 20mph speed limits. There was also cross-party support within the council with only the Tories objecting (and one of them called for more roads at 20mph in his ward, after he had voted against the city wide limit). The local chip wrapper did try to play up the “mass protest march” against 20mph, however this turned out to be 47 people organised by a taxi business. The police didn’t need to estimate the numbers which the organiser would then claim to be double. They just did a head count, as did an independent observer who said there were only 43.

Despite this evidence the politicians keep saying that reducing the national speed limit in built up areas to 20mph is unpopular with the electorate, so the question is, is 20mph so unpopular? In a recent poll commissioned by the Royal College of Paediatrics and Child Health, found that 58% of Britons “support reducing the national speed limit in built up areas to 20mph to attempt to reduce deaths from road traffic accidents”. The RCPCH recommend that we should: “Encourage physical activity for all children and young people – with and without disabilities – by creating more cycle lanes and promoting 20mph speed limits” and “Reduce the national speed limit in built up areas to 20mph to reduce the number of deaths by road traffic accidents”.

Edinburgh has now committed to doing something which Graz in Austria managed to do 23 years ago. Now if we could just get just Edinburgh to pick up a few other ideas from cities across Europe, maybe Zurich’s policy of one car out, one car in? But then that would need the City of Edinburgh Council to have the ambition to make Edinburgh a world class city.

Possibly Related Posts: (automatically generated)

You might not realise it, but today is the World Day of Remembrance for Road Traffic Victims, which takes place on the third Sunday in November every year as the appropriate acknowledgement of victims of road traffic crashes and the victims’ families. It is estimated, worldwide, that 1.2 million people are killed in road crashes each year and as many as 50 million are injured. I was going to list all the people I have personally known who have died on the roads, members of my extended family, friends and acquaintances. But by the time I had got to 20, I was finding it all too depressing and so abandoned the idea. Too much loss, too much pain.

The theme for this year is “Speed kills – design out speeding”

For some years now, along with the Pedal on Parliament campaign group, I have been advocating the idea that the statutory speed limit for built up areas in Scotland should be lowered from 30mph to 20mph. This would undoubtedly save lives and make Scotland a better place to live. Not only would it be relatively cheap to do, but it is also within the gift of the Scottish Parliament. The power to vary speed limits was devolved, along with the power to vary the drink-driving limits, as part of the Scotland Act (2012). The Scottish Parliament has exercised the power to change the drink-drive limit, from 5th December 2014 the permitted blood alcohol limit for drivers will be cut from 80mg to 50mg in every 100ml of blood. This has to be a good thing. However, the powers to vary speed limits has, so far, only been used to raise the speed limit for heavy goods vehicles using the A9. This is a retrograde step as Holyrood does not have the power to change the Laws of Physics, and therefore this will in no way make the A9 a safer road.

As I have said elsewhere, it has been known for well over 30 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
At 20mph just 3% of pedestrians or cyclists are killed

The difference just a few miles per hour makes

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. Then it takes time to actually stop, and to stop safely drivers have to think ahead rather than just try to react to the situation. Lowering the speed limit allows drivers more time to think and therefore reduces the frequency of accidents collisions. There are people out there who think that they are a good drivers and that it wouldn’t happen to them – I would suggest that they read about the experiences of this Hertfordshire GP, who used to think it wouldn’t happen to him.

Once again, I call on the Scottish Government to lower the statutory speed limit in built up areas from 30mph to 20mph, this will save lives. If you agree with me write to your MSPs today and tell them so.

This post also appears on the Pedal on Parliament website, in a slightly modified form.

Possibly Related Posts: (automatically generated)

We know that the health benefits to society from cycling outweigh negative impacts by up to a factor of 20. We know that cities with higher levels of cycling are more attractive places to live, work and do business. I have discussed before in this blog how to achieve this, it is not rocket science, as this recent report from the International Transport Forum at the OECD shows. They recommend reducing “urban road speeds to 30km/h [20 mph] or less, and the use of separated cycling infrastructure to increase the number of new cyclists. Attracting new cyclists gains the greatest health benefits through increased physical activity, including reducing risks linked to cardiovascular disease, obesity and Type-2 diabetes.”

So why aren’t we doing more to encourage cycling in Scotland? It’s one of the fundamental duties of any government to protect the lives of its citizens. However, here in Scotland, both national and local government drag their feet on these issues. I have sat across the table from the Scottish transport minister and asked him to use the powers which have been devolved to the Scottish Government, to lower the national speed limit in built up areas (defined as places where the street lighting columns are < 185 m apart) from the current limit of 30 mph to 20 mph. This is would at a stroke save lives. However, he has refused point blank to do so, saying that it would take away powers from Local Authorities (LAs). This argument is utter nonsense as LAs have the power to raise or lower speed limits on individual roads as they see fit. So the real effect on LAs would be that they would have to justify to the voters why they wanted to raise speed limits in built up areas, where people live, work and shop, from 20 mph to 30 mph. It is well known that 20 mph speed limits are popular with people who live next to the roads where these limits apply. Therefore, it may prove difficult for LAs to raise the limits, but that's Democracy for you.

Here in Edinburgh, there has recently been an announcement from the City of Edinburgh Council that it intends to lower the 30 mph speed limit to 20 mph, across the whole city, but not until 2017. Why 2017? You may well ask, well for one thing, it is after the next local elections. Also it gives them three years in which to try and find justifications to maintain the higher 30 mph speed limit on “key arterial roads”, even though these pass through some of the most densely populated parts of the city.

Why are our elected representatives not acting in the best interests of the people? Why are they not taking simple steps to protect the health and lives of the citizens they are elected to represent? The only answer can be moral cowardice! For this reason I urge you all to join the Pedal on Parliament protest on the 26th April 2014 to send a message to those who have the power to change things – now is the time to grow a spine and show some moral backbone!

Possibly Related Posts: (automatically generated)

Following the successful trial 20 mph speed limit zone in South Edinburgh it has finally been decided to broaden this out to the whole city and not before time. However, there are still a few out standing questions: will all roads in the city be included? If not what will be the criteria for having roads with higher speed limits? Will there be enforcement of the speed limits within the city?

While the trial 20 mph speed limit zone on the Southside has proved to be popular with those living in the area, there have been a few issues. To start with during the consultation before the trial zone was started, the Community Councils and the majority of local residents (who responded to the consultation) asked for the major roads, which also had the highest collision rates, to be included in the trial. However, this was refused due to objections from Lothian Buses, although there was no evidence published that this would significantly affect bus timetables or overall journey times. Another issue has been the reluctance of the police to enforce the 20 mph speed limits, as a result average speeds within the trial area have only been reduced by only 2mph, with the majority of driver flouting the speed limits. In spite of this the 20 mph trial has been overwhelmingly welcomed by the residents of the City.

The most frustrating part of all this is that we know metropolitan wide speed limits work, they are not a new idea Graz in Austria was the first city in Europe to introduce them in 1992 (they saw an immediate 25% drop in the number of serious collisions as a result, although this did rise later when enforcement was relaxed). In 2008 Portsmouth became the first city in the UK to adopt the a blanket 20 mph speed limit, which has also significantly reduced the number of collisions (even if the motoring lobby like to pretend that it doesn’t, but then they regard dead children as collateral damage and a price worth paying).

Fortunately the City of Edinburgh Council has now agreed that there should be 20 mph speed limit zones across the city, but just which streets will be included is yet to be decided. We are told that there will be a consultation, well yes we had one of those before the Southside trial was introduced. There was strong support from the Community Councils on the Southside for the pilot, and people would have liked more streets to be included, they were over ruled because Lothian Buses objected to certain roads being included, claiming bus services would be slowed (although the evidence for this was never published). We are supposed to be in a Democracy where the people and not business should have the final say. We are also told that the transport and environment committee has agreed to roll out 20mph limits to all residential streets, main shopping streets, city centre streets, and streets with high levels of pedestrian and/or cyclist activity. Which begs the question how do you define a “residential street” in a city like Edinburgh, which has very few commercial dead zones (unlike, say Glasgow, where large swathes of housing were demolished to make way for urban motorways). If you travel along any of the major routes to the city centre there are people living along these streets. So who will have the final say on what speed limits apply to the major arterial routes, the people that live there or a bus company (who director live in the leafier parts of town where the streets are already traffic calmed)? Apparently Councillor Joanna Mowat has already asked for a definition of a residential street. She said: “People will say ‘I live here, so it’s a residential street’. It will be interpreted in different ways.”, however her question appears not to have been answered, yet.

Then there is the issue of enforcement, in the current trial, Lothian and Borders Police (now Police Scotland) refused to implement effective enforcement of the 20 mph speed limit. Sadly Police Scotland lack the integrity of the likes of Julie Spence who condemned speeding as being middle class’s version of antisocial behaviour with motorists convinced they should be “able to get away with” breaking the law. Councillor Lesley Hinds is on record as saying that “We want to encourage drivers to keep their speed down and get used to that, rather than fining people.” Why? We don’t take this approach with other forms of anti-social criminal behaviour, why should we tolerate it from people just because they hold a driving licence? She also says “educating drivers was one of the most important ways forward”, well Lesley all drivers have been taught to drive within the speed limits, it is one of the requirements of the driving test, I used to be a full qualified Approved Driving Instructor, I used to teach people how to do it. People know that speeding is wrong, so they should expect to be fined if they break the law, the most effective way of getting people to comply with the law is to enforce it. No Excuses!

Another thing we can learn from the Graz experience is that public support support for 30Km/h limits dropped during the consultation period before the introduction of the lower speed limits. Before the conciliation there was 64% support, during the conciliation this dropped to 44%, however within a year of the lower speed limits being implemented support had risen to 60%, and two years later had reached 80%. For the majority of people having lower speed limits is welcome, it is only the selfish few who want to put the lives of others at risk, for their own convenience. By the use of rigorous enforcement, we can make speeding less socially acceptable. We just need our elected representatives to show some spine in the face of the morally bankrupt motoring lobby. Just remember why there are speed limits:

  • 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

Once they have taken that on-board, maybe they could have get a few lessons on how to deal with the problem of cars parked illegally in cycle lanes

Possibly Related Posts: (automatically generated)

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:

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.

Addendum: The above data on death rates includes children, in resent years groups such as RoSPA have taken to excluding children from their data, in order to play down the risk from motor vehicles. I find this practice utterly disgusting.

Possibly Related Posts: (automatically generated)

We proudly support Earth Hour.    Use WordPress too? Get the plugin.
Bear