Speed reduction

Speed reduction methods to promote road safety and save lives

Published: 2017-03-09

The traditional road safety benefits of lower vehicle speeds include saving lives and reducing the impact and likelihood of crashes. However, speed reduction has important additional benefits that increase the quality of life for society at large. These benefits include a reduction in traffic noise, pollution, green house gases, average fuel consumption and barrier effects. Moreover, these effects will encourage cycling and walking that have wider health benefits for society. Speed reduction thus pays off in numerous ways.

Speed reduction measures fall into the following categories: direct – infrastructure, vehicle technology and enforcement and indirect – education and publicity. For this blog we will focus on the direct speed reduction measures. However, the importance well-structured traffic education policies and effective and constant publicity should not be underestimated. They serve to maintain awareness among the driving public of the dangers of speeding and the advantages of speed compliance.

Infrastructure adaptations for speed reduction

An important measure to reduce speeds is the implementation of traffic calming infrastructure based on Vision Zero and Sustainable Safety*. This means a strategic review of infrastructure design criteria and infrastructure changes at high-risk locations. Such measures include:

1. Speed humps and raised platforms

Speed hump for speed reduction
Speed hump for speed reduction
Raised pedestrian crossing in Hahndorf, South Australia

2. Gateway infrastructure treatments indicating a new speed regime e.g. when entering an built-up area, residential areas or school zones from a higher speed or access road

Gateway infrastructure treatments in the UK. Source: SABRE – www.sabre-roads.org.uk

3. Roundabouts slow traffic at intersections, positively change the potential impact angle, provide better visibility and provide clarity about traffic flow and the right-of-way

Roundabout Purmerend, The Netherlands. Source: Archie Europe Rotonde Cam
Roundabout Purmerend, The Netherlands. Source: Archie Europe Rotonde Cam 

4. Pavement narrowings and optical treatments present a feeling or even illusion that the driver is going too fast.

Various narrowing and optical methods to reduce speeding

Vehicle technology to reduce speeding

Intelligent Speed Adaptation (ISA) involves any system that ensures that the speed of a vehicle does not exceed a safe and/or legally enforced speed. The information on potential speeding comes from sources such as GPS location, road maps, radio beacons, optical recognition (e.g. speed signs) and dead reckoning techniques. In case of speeding and depending on the type of system, either the driver can be alerted or the speed can be reduced automatically. These two types of ISA systems differ in that passive systems only warn the driver of the vehicle travelling at an unsafe speed, while active systems automatically intervene and correct the speed to conform with the safe or legal speed limit. Most active ISA systems allow the driver to override the system when deemed necessary. This is likely to improve acceptance , but will also increases the risk of speeding. The ETSC (European Transport Safety Council) has been advocating the benefits of Intelligent Speed Assistance (ISA) for many years. Euro NCAP (New Car Assessment Programme) decided to reward extra points for vehicles that include ISA since 2009.

Enforcement to improve compliance with speed regimes

The previously discussed methods  seek to prevent speeding. Enforcement is an corrective method applied after speeding by punishing the violating driver, mostly by means of fines and/or the through the drivers license point system. Enforcement can be manual of automatic, overt or covert, mobile or stationary.

Manual enforcement mostly takes place overtly or covertly by police officers or other authorised officials confronting violating drivers by stopping them on the spot after a violation is registered from a driving in-vehicle or stationary position along the road. This type of enforcement is effective but tends to be quite inefficient due to the high labour content of the operation.

Average speed enforcement along the A2 motorway in the Netherlands


Clockwise: Spot camera, average speed and automated in-vehicle enforcement

Assuming an owner liability legal regime, automated camera enforcement can be executed in an efficient operational arrangement where printed violations warnings are sent directly to the vehicle owner’s address without any human interference. With driver liability used in e.g. the Nordics, Germany, Switzerland and Japan processing is a bit more complicated due to the facial matching requirement for the evidence. When implementing automated enforcement requires a suitable legal regime, a reliable up-to-date vehicle registration and a well coordinated and managed government apparatus. Legal integrity and measurement accuracy should be guaranteed by independent type approval and regular verification. This presents the judiciary with in autonomous yardstick in case of legal challenges to violations. Automated enforcement systems are available in many different types with various detection methods such as radar, laser, piëzo and loops each with its advantages and disadvantages. Off all these detection technologies radar detection provides the best compromise offering limited occlusion, no road surface damage, high mounting option, less vandalism, no soiling  and low maintenance. Automated speed enforcement can be operated in a mobile, in-vehicle, semi-fixed, fixed and average speed arrangement. The latter does not measure, but calculates the speed by clocking  time over a measured distance between entry and exit cameras.

Mobile, semi fixed and spot speed camera enforcement


With the three options presented there is no single best solution. These three speed reduction methods should be applied simultaneously. For instance, speed humps are misplaced to reduce speeding on motorways and national roads. Also, in narrow curvy streets in residential neighbourhoods the benefit of fixed speed cameras is limited. Speed humps and chicanes are more relevant to encourage compliance with 30 km/h speed residential limits. Most vehicle manufacturers offer ISA systems, increasingly as a standard safety feature. One of the key aspects to improve road safety is to reduce the average network speed of all vehicles. All three methods mentioned can play a significant role in achieving that.


* Sources

  1. Vision Zero – http://www.visionzcom/making-mobility-safe-from-the-start/
  2. Sustainable Safety – https://www.swov.nl/sites/default/files/publicaties/gearchiveerde-factsheet/uk/fs_sustainable_safety_background_archived.pdf
  3. IRAP – http://toolkit.irap.org/default.asp?page=treatment&id=33
  4. ISA – http://etsc.eu/intelligent-speed-assistance-isa/ https://ec.europa.eu/transport/road_safety/specialist/knowledge/speed/new_technologies_new_opportunities/intelligent_speed_adaptation_isa_en
  5. SWOV Speed enforcement – https://www.swov.nl/en/facts-figures/factsheet/police-traffic-enforcement https://www.swov.nl/sites/default/files/publicaties/gearchiveerde-factsheet/uk/fs_speed_cameras_archived.pdf




Philip Wijers

Published: 2017-03-09

Filed under: Enforcement, Speed reduction