Is traffic calming effective?


Area-wide traffic calming schemes and 20mph zones are very effective in reducing vehicle speeds, and thereby reducing road death and injury.

A review of accidents in 72 20mph zones found that average mean speeds were reduced by 9mph, from 25mph to 16mph in the zones. On average, for every 1mph speed reduction, there was a 6.2% accident reduction. All road accidents in the zones fell by 61%, and there was no evidence of accident migration onto surrounding roads. Traffic flows in the zones reduced by 27%. The effects were particularly significant for the most vulnerable road users:

  • All pedestrian accidents down by 63%
  • All cyclist accidents down by 29%
  • Motorcyclist accidents down by 73%
  • Child accidents down by 67%
  • Child pedestrian accidents down by 70%
  • Child cyclist accidents down by 48%.

A review of more than 100 20mph zones in London also found that they were very effective in reducing road injuries to children. In the zones, speeds were reduced by 9mph and traffic flows by about 15%.

Road casualties in the zones were reduced by 45% and fatal or seriously injured casualties by 57%. Again, significant protection was provided to the most vulnerable road users:

  • Pedestrian casualties down by 40%, and pedestrians killed or seriously injured (KSI) down by 50%
  • Child pedestrian casualties down by 48% and child pedestrians KSI down by 61%
  • Cyclist casualties down by 33% and cyclist KSI down by 50%
  • Child cyclist casualties down by 59% and child cyclists KSI down by 60%
  • Car occupant casualties down by 57% car occupant KSI down by 77%
  • Child car occupant casualties down by 51% and child car occupants KSI down by 47%.

You can find more information about traffic calming on the Direct Gov website.

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