Traffic Calming – Vehicle Activated Speed (VAS) Limit Reminder Signs

  • Published: TRL, 1995a
  • Authors: D.C. Webster
  • Date Added: 05 Feb 2013
  • Last Update: 25 Oct 2016
  • Format: html


To review the published results from 13 of these 'secret' sign sites which have been used in the UK, other European countries and the USA. Single 'secret' signs were used at ten sites and a pair of 'secret' signs were used at three of the sites.


Published data on vehicle speeds was reviewed to assess the impact of the ‘secret’ signs on mean and 85th percentile speeds.

Key Findings:

  • VAS appear to reduce speeds by a few mph at the sign and some of the reduction can be maintained some distance downstream in the village centre.

  • Changes in RTIs, while not statistically significant were still encouraging – when compared to control sites there was an overall reduction in RTIs of 42 per cent.

  • The speed reductions appeared to be maintained over time.


Speed reduction, Non-physical measures.