Mobile Vehicle Activated Signs

Mobile Vehicle Activated Signs (MVAS) are electronic signs which only become visible when approaching motor vehicles are exceeding a certain speed. The signs normally display the speed limit, however they can also display the actual speed on the sign and these are called Speed Indicating Devices (SID).

MVAS are formed of many bright lights which only turn on when the target motor vehicle is in plain view of the sign.

A black sign with 'slow down' and '30' speed limit in lights
Mobile Vehicle Activated Sign (MVAS)


MVAS have a short-lived effectiveness in reducing speeds. Unfortunately drivers become too familiar with them when they are situated in one particular location for long periods of time. They can be most effective when positioned near downhill gradients reminding drivers who may be inadvertently speeding.

When MVAS are relocated regularly around different parts of the village or town this can increase effectiveness as drivers will be unaware of where the sign will be next time they travel.

Advantages of Mobile Vehicle Activated Signs

  • No discomfort or delay experienced by any vehicle user
  • Relatively cheap
  • Continue to have a positive effect over time if relocated regularly
  • Moving between different sites can increase effectiveness

Disadvantages of Mobile Vehicle Activated Signs

  • Not as effective as vertical interventions
  • Too many of these devices could diminish their effectiveness


  • Parish and town councils would be required to maintain and relocate the signs going forward in accordance with Cambridgeshire’s Highway Asset Management Policy.
  • Location of the MVAS needs careful consideration as light pollution can cause concerns with residents
  • MVAS must be placed on a straight stretch of road to allow the radar device to accurately judge the speed of approaching motor vehicles

Cost of installation

Equipment = £3,000 - £4,500
Works = £1,000 - £2,500
Total = £4,000 - £7,000

Please note that costs above are to supply the MVAS, associated mounted equipment, spare batteries, and supply and install a number of posts for the device to be moved around.

Apply for permission to install MVAS

We recognise that MVAS can be a popular speed educational tool. Should you wish to apply for permission to use them on the highway please complete this application form and return by post to the address specified or by email to

You will be required to agree to a Memorandum of Understanding to make sure the sign's correct use on the highway.