Twenty’s plenty

I’ve always thought of the 30 mph speed limit in London as having been imposed since the dawn of time.

The recent seemingly draconian measure by many local authorities to reduce this to a blanket 20 mph to many is a novel and unnecessary step.

Yet for many years 20 mph was the norm it being introduced 80 years ago.

[S]tatically for every 1 mph reduced in the average speed there are 6 per cent fewer accidents according to the Department for Transport who say that the limit imposed should be seen by drivers as the maximum speed rather than as a target to achieve irrespective of road conditions. The limit seems to have been successful with 1 death on the roads for every 20,000 cars.

There was a blanket 20 mph speed limit for decades at the start of the last century presumably once the requirement for vehicles to be preceded by a man carrying a red flag.

In 1903 the Motor Car Act made 20 mph mandatory. Presumably at that time a vehicle’s maximum speed was less than 50 mph, and had a stopping distance equivalent to a super tanker.

When in 1930 this Act was repealed carnage on Britain’s roads ensued. By 1034 with only one-tenth of the cars on the road compared with today’s traffic there was 4 times as many deaths.

A controversial Act was passed imposing a 30 mph speed limit, just how that figure was agreed has been lost in the mists of time and as with all British compromises chaos ensued.

Pieces of paper were plastered over existing signs, or tin discs used. Where authorities had managed to erect a regulatory sign these were often torn down, some ended up in lakes.

Now with greater traffic volumes and the huge increase in cyclists on London’s roads the debate has been re-ignited.

The Lib-Dems considered a 10 mph maximum in some areas, while many more pragmatic types of council have opted for 20 mph in residential streets supplementing this with as many road obstacles as it’s possible to imagine.

At 20 mph, if we adhere to Department of Transport guidelines, our average speed should be around 17–18 mph about the rate of travel for more sedate cyclists.


Unfortunately the modern car (or cab) hasn’t been designed to be driven at a continuous 17 mph. The gear ratios are incorrect, fuel consumption higher and engines emit more particulates. In a world of electric cars this wouldn’t be a problem.

Failing this utopian world the most effective way I’ve seen is the average speed camera. Only a fool and the thief would fail to comply with the speed limit under those watchful eyes.

Local authorities will just have to bite the bullet and invest if they want everyone traversing their land adhering to their diktats.

2 thoughts on “Twenty’s plenty”

  1. The new speed limit is unlikely to make much difference in town where weight on numbers in any case brings average speeds down to a crawl. In those areas, 20 mph would be seen as an improvement!

    I think this is part of the problem: congestion causes frustration and frustration tempts drivers to put their food down whenever they encounter clear space, even if it’s only a few yards long. This impatience causes such misdemeanors as running lights that have just turned red and thus running over pedestrian crossings when the green man is showing or blocking crossings when caught in tailbacks. Motor vehicles and pedestrians don’t mix. As long as they share the same space, there will be accidents.

    We now have the added complication of increasing numbers of cyclists. Many of these are people without any real understanding of the rules of the road or any intention of obeying them. Increasing numbers of cyclists will mean increasing numbers of dead and injured cyclists. Speed limits will do very little to limit cyclist casualties given the reckless behaviour of cyclists themselves.

    I used to drive and I used to cycle. I am therefore not anti-motorist or anti-cyclist but I do often shake my head in disbelief at the behaviour of both those groups of road users.


    1. Yes I’m often astounded just how inconsiderable the motorist is towards the cyclist. Likewise many cyclists seem to have a death wish, wither for themselves or for pedestrians.


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