Monday , November 19 2018
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Slow down but not too slow

When it comes to speed limits, it seems the only direction is down. Many built-up areas are already a low 20mph. Yet one driver gets caught for speeding every 75 seconds in the UK. Speed limits are supposed to reduce the chance and severity of an accident. But is there any evidence speed limits, especially low, actually stop us from speeding?

Recent UK stats show the opposite. Motorists are more likely to speed when limits are low:

  • 16% do more than 30mph on 20mph streets.
  • 53% exceed the maximum in 30mph areas
  • 46% drive faster than 70mph on motorways
  • 8% go over 60mph on single carriageway roads.

In fact, where UK councils had installed 20mph zones, seven of 13 areas saw an increase in rates of people killed or seriously injured. Perhaps the locals felt safer in those zones and took less care. One Department for Transport spokesperson even said 20mph zones “did not work in most areas” and even claimed drivers “don’t believe in them”.

Many Australian drivers would baulk at the kilometre equivalent of 20mph, which is 32kmh. They already find 40 kmh school zones mind-numbing. Speed surveys show 40kmh school zones have the lowest rate of compliance – only 40% of drivers keep within the school zone speed limit. Yet penalties for traffic offences in school zones are even higher than in other zones.

UK police have just launched an official review of the 10% plus 2mph buffer zone. One Chief Constable said allowing drivers this buffer zone before being prosecuted gives the mistaken impression it is fine to speed.

The way authorities enforce the rules suggests speeding drivers have poor attitudes and always intend to speed. But speeding is not always deliberate.

One university study found any kind of interruption in a low limit zone can lead to “prospective memory error”. For example, a traffic light turning green during roadworks causes drivers to resume their usual speed, not the roadworks speed. There are no cues to remind them. In fact, the study found drivers do slow down if they get an immediate reminder.

Prospective memory error can apply during roadworks or when driving from rural to urban speed zones. However, these academic arguments don’t seem to have much effect on current law enforcement.

The usual punishment for speeding is penalty points and a fine but speeding awareness courses may be more effective. Ipsos Mori analysed the records of 2.2 million UK motorists and found 1.4 million chose a speed awareness course while 192,000 took penalty points and a fine. It discovered:

  • Participants are 23% less likely than those who took penalty points to be caught speeding in the six months after the course
  • 21% of course sitters compared to 23% who take points reoffend within three years.

In other words, speeders do change their behaviour but eventually return to their usual habits. We suspect there is a lot more to speeding than a group of rebellious motorists deciding to go over the limit.

In the battle against speeding, it is perhaps strange that nothing is being done to improve driver training. Authorities assume, once we pass the test as an adolescent, we know what we’re doing from then on. This is in spite of driving conditions changing markedly in the course of somebody’s driving life.

As more and more roads adopt low speeds, we may wonder why it’s worth driving at all.

Corrina is content manager for, an online resource about green slips, but she likes to write about car stuff too.

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