It’s essential that legal speed limits are enforced, to ensure people are obeying the law and not putting themselves and others at risk. There are two traditional ways to enforce speed limits: speed cameras (fixed or operated by police) and traffic calming. Intelligent speed adaptation (ISA), as discussed below, is a promising technology that could enable greater enforcement of speed limits and greatly improved road safety as a result.
There are different kinds of cameras:
- fixed cameras that measure the speed of passing cars and take photographs of those that break the speed limit
- mobile cameras held by police officers, placed on tripods, or fixed in police cars, that can visit different locations
- average, or time-over-distance, cameras, that calculate the time it takes a vehicle to travel between cameras and therefore the average speed.
Average cameras have commonly been used on long stretches of fast roads, but it is now possible to use them in towns and villages too, including over small networks of roads such as housing estates . They are particularly beneficial as they enforce limits over a longer stretch of road, preventing law-breaking drivers from being able to speed up again immediately after passing a camera.
Benefits of speed cameras
Speed cameras are not only cost-effective, but carry a significant cost-benefit to the public purse. Installation, maintenance, and administration can be self-funded by fines, if this money is ring-fenced to re-invest into road safety measures (although this is not always the case: in the UK fines go straight to central government, but are not reinvested in cameras or other road safety measures). Cameras will also pay for themselves several times over in the money saved to the economy by preventing deaths and serious injuries: road crashes were estimated to cost the economy £16.3 billion in 2014 due to human costs and costs to emergency, health and criminal justice services .
Cameras can catch far higher numbers of speeding drivers than traffic police with mobile cameras, and at much lower cost, freeing up police for other duties that cannot be conducted by technology, such as breath-testing.
Effectiveness of speed cameras
There is overwhelming evidence that speed cameras are effective in reducing speeds and preventing crashes and casualties. For example:
- A four-year national evaluation of more than 4,000 speed camera sites across the UK found a 70% reduction in speeding at fixed sites, a fall of 6% in average speeds and a 42% reduction in deaths and serious injuries .
- Researchers at Liverpool University developed a mathematical model which proves that speed cameras substantially reduce crashes, even when accounting for random fluctuations in crash levels (known as ‘regression to the mean’) .
- Analysis of data from 551 fixed speed cameras across England found that fatal and serious collisions dropped by an average of 27% in their vicinity following installation .
- Annual deaths and serious injuries dropped 68% at all 408 speed camera sites in Scotland, when comparing the three-year average post-installation with the three-year average prior to installation .
- A review of 35 international studies into the effectiveness of speed cameras found that speed cameras reduce average speeds by 1-15% and serious and fatal crashes by 11-44% .
Support for speed cameras
The majority of people accept that speed cameras do a good job of reducing speeds and saving lives. In the UK, four in five (80%) drivers support speed cameras and 79% agree cameras have helped reduce road deaths .
A Brake and Direct Line survey found almost two in three (62%) drivers said more enforcement, including cameras and traffic police, would persuade them to take more care on the road .
There is still a small minority that consider speed cameras and speeding fines an “unfair charge on motorists”. This is clearly not the case, as only drivers who break the law by speeding are penalised – if you don’t break the speed limit, you won’t get caught by a camera.
Traffic calming, including bumps, humps, bollards, chicanes, markings, and bigger or vehicle-activated speed limit signs, are designed to slow down drivers to within the posted limit, often within built-up and residential areas. Other measures include giving the road environment the look and feel of an area used by lots of people, encouraging drivers to think they ought to slow down, such as making the road surface coloured or rough, or installing wide pavements with benches and flower pots.
Traffic calming often carries a higher initial cost than a camera but, if implemented carefully, can be very effective. In towns and villages in the UK where 20mph speed limits have been implemented, the speed of traffic has dropped most when traffic calming measures have also been installed, such as in the city of Hull .
There are also measures that can slow down traffic on country roads, particularly where drivers are failing to perceive danger and not slowing down enough. These include road markings, rumble strips, and vehicle-activated signs. One study found that vehicle-activated signs on country roads could reduce speeds by 5km/h (3mph) and crashes by 70% .
Intelligent Speed Assistance
Intelligent Speed Assistance (ISA) is an Advanced Driver Assistance System (ADAS) that is designed to prevent drivers from exceeding speed limits and is proven to work.
ISA works by using GPS combined with a digital map of speed limits to keep vehicles to the posted speed limit on each road. However, there are three types of ISA, with distinct ways in how they help achieve speed compliance:
- advisory ISA gives the driver immediate feedback through a visual, audio or haptic signal if the speed limit changes or they exceed the speed limit
- voluntary ISA automatically decreases acceleration if the driver exceeds the speed limit, but the driver can override this
- mandatory ISA automatically decreases acceleration if the driver exceeds the speed limit, and cannot be overridden
- Read our advice for drivers on staying slow and safe
- Back our GO 20 campaign for lower speed limits in towns, cities and villages
- Back our Rural roads not racetracks campaign for lower speed limits on country roads
- Read our fact page on speed limits and stopping distances
- Read our fact pages about speed in communities, on country roads and on motorways
 SPECS3 is now Home Office Type Approved, Transport Business International, 2009
 Reported Road Casualties Great Britain 2014, Department for Transport, 2015, table RAS60003
 The national safety camera programme: Four-year evaluation report, PA ConsultingGroup, UCL, University of Liverpool and Napier University, commissioned by the Department for Transport, 2005
 Speed cameras do reduce accidents, say researchers, Phys.org, 2008
 Deaths and serious injuries down a quarter near speed cameras, RAC Foundation, 2013
 Key Scottish Safety Camera Programme Statistics 2011, Scottish Government, 2012
 Speed cameras for the prevention of road traffic injuries and deaths, Cochrane Injuries Group, 2010
 Speed cameras: a snapshot of drivers’ opinions, Institute of Advanced Motorists, 2013
 Report on safe driving: speed, Brake and Direct Line, 2010
 Memorandum by Kingston upon Hull City Council: 20 mph zones in Kingston Upon Hull, Select Committee on Transport, Local Government and the Regions, 2002
 Methods for Reducing Speeds on Rural Roads, Austroads, 2014
Page last updated: September 2014