Road Network Operations
& Intelligent Transport Systems
A guide for practitioners!

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Policing / Enforcement

Policing and enforcement have an important part to play in road network operations to improve road safety and to support the efficient use of road space. ITS provides the capability for automated detection and registration of traffic offences such as:

  • speeding
  • diving through a red light
  • close following of vehicles in tunnels
  • safe driving hours for trucks
  • unlicensed and unregistered vehicles
  • vehicles without insurance
  • vehicle owners with outstanding fines
  • overloading enforcement

Camera-based ITS solutions can be used for vehicle access control, enforcement of low emission zones (“clear zones”) (See Environmental and Resource Issues) and traffic offence detection (over height, overweight), as well as moving vehicle offences (speeding). Pictures are automatically taken of vehicles/drivers that violate the rules and a fine is sent to the owner/driver.

Camera-based applications which incorporate Automatic Number Plate Reading (ANPR) include the prevention of through traffic on inappropriate roads (rat running) - such as bus only lanes, residential streets and short-cuts through hospital grounds. By installing ANPR at the control points, details of vehicles entering and leaving can be captured. The availability of a well-maintained and reliable up-to-date vehicle registration database is essential.

Automated enforcement systems for speed limit and traffic signal compliance have proven to be very effective in reducing fatalities and can create increased customer demand for speed alert systems. Many road authorities are now looking at the best ways to promote the deployment of ITS based automated enforcement systems on their roads. Special attention to enforcement on road sections with dynamic speed management (variable speed limits) is required.

Administrative arrangements and legal issues differ from country to country and will dictate enforcement methods and procedures. For example in some countries the vehicle owner is responsible for the offence whoever is driving; whereas elsewhere the police may have to prove who is the driver – so that the enforcement camera image has to show the driver’s face. Privacy issues relate to systems that either identify the driver (enforcement systems) or their location. These are often subject to legislation that limits the capture, use and storage of data (See Law Enforcement).

The European Union’s PEPPER project (2006-2008) is an example of a collaborative study which looked at police enforcement policy and programmes across European roads with the aim of improving its efficiency. (See

PEPPER assessed several aspects of enforcement in relation to speeding, drink-driving and use of seat belts– and focused on:

  • detection of infringements
  • administrative and legal handling after infringement
  • effects of enforcement on road user behaviour and accidents
  • enforcement methods and tools
  • collection of enforcement data

Speed Enforcement

Traditional forms of speed enforcement (such as Gatso wet film cameras) are being superseded by digital photography, eliminating the need to replace the film and requiring lower maintenance and operational costs.

Static speed enforcement measures (spot speeds) can cause rapid acceleration and deceleration as drivers apply their brakes in advance of cameras and then speed up. Average speed enforcement is enabled by Automatic Number Plate Recognition (ANPR) systems which identify vehicles at different positions on the network so that the average speed between two points can be measured. In this way, the speed across the entire length of a road can be enforced, to encourage compliance over longer periods, particularly through areas of temporary traffic management where operatives may be present.

A number of road safety benefits are associated with average speed enforcement. There are generally higher rates of compliance with speed limits with reductions in average and 85th percentile speeds (the speed exceeded by only 15% of drivers) and lower speed variability between vehicles – with consequential reductions in accident rates and in particular, serious and fatal injuries.

Most current enforcement technologies (such as speed warning devices) do not provide feedback to the driver on how they compare with others. Feedback based on collective measures of performance (such as the frequency and level of speeds in excess of the limit) can be significant in changing driver behaviour and improving compliance. The assumption is that most drivers will wish to improve their performance and conform to the actions of others. An ITS solution can use the individual data to provide drivers with an accurate overview of enforcement activity and encourage further compliance.

Technology, Data & Resources

Spot Speeds

ANPR is a method that uses optical character recognition of digital images to read the licence plates on vehicles. The images are captured on cameras located in a mobile unit or built into law enforcement vehicles or from Closed Circuit Television (CCTV). The ANPR system cross-references the data against existing vehicle registration databases to determine whether the vehicle is untaxed, unlicensed or of any other interest to the police.

Camera errors can be as a result of:

  • poor image resolution (if the number plate is too far away);
  • blurry images (motion blur, mobile units);
  • poor lighting and low contrast;
  • objects obscuring (part of) the number plate (vehicle tow bar, high sided vehicles);
  • unusual fonts on custom-made number plates;
  • circumvention techniques (to obscure number plates – such as reflective lettering).

Average Speeds

Average speed cameras operate using automatic digital technology. Cameras are mounted on columns at the side of the road. By placing the cameras at known points the speed of vehicles can be monitored along a length of road. The cameras are linked by cable or wireless and continuously capture images of vehicles. The number plates are read using ANPR and the average speed of the vehicle between the two cameras is calculated. If this exceeds the speed limit, an offence record is created and the owner contacted with reference to a database of vehicle registrations.

Despite the success of average speed cameras, their use of ANPR highlights a number of practical, social and political issues:

  • fears of misidentification - errors within the vehicle licence database can occur due to delays in updating
  • limitations with the APNR technology itself – such as failure to capture the number plate, incomplete capture (failure to read all the characters/misreading characters)
  • capturing the number plate twice on different cameras on multilane highways as the vehicle switches lane all present problems

“Clock drift” is another phenomenon that may affect reliability, whereby the physical timing mechanisms that are part of the ANPR system as a whole are subject to errors. These can happen for a number of reasons, including temporary power cuts. The subsequent ANPR data may be ‘fast’ or ‘slow’. The set up on the systems can vary and some include an automatic clock readjustment process. The size of the timing errors can be anything from less than 2 minutes to over 8 minutes. This undermines public confidence in using ANPR for speed enforcement and evidence of a speeding offence.

DrunK- driving enforcement

Alcohol consumption, even in relatively small amounts, increases the risk of being involved in an accident for motorists and pedestrians. Alcohol not only impairs critical cognitive processes, such as vision and reaction time, it is also associated with impaired judgement. Road users under the influence of alcohol engage more in other risky behaviours such as crossing traffic in inappropriate places, or not using a vehicle seat-belt where madatory.

Research indicates that a considerable proportion of drivers, motorcyclists and pedestrians have alcohol in their blood in sufficient concentrations to impair their skills – whilst the probability of arrest while driving with an illegal blood alcohol level is low.

Traditional methods of reducing the prevalence of drink driving have included fines, prison sentences, vehicle impoundment and licence revocation – each has a downside. Prison for example is costly.

There is therefore an opportunity for ITS to play a part in the detection of drunken driving. Improvements in alcohol-sensing technology have led to the development of alcohol ignition interlocks. To operate a vehicle equipped with an interlock, the driver must first provide a breath specimen. If the breath alcohol concentration of the specimen is too high, the vehicle will not start.

Convicted drink drivers are sometimes offered the choice of a standard punishment (fine or points on their licence), or have the option for an alcohol ignition interlock to be fitted to their vehicle for a fixed period. Interlocks are typically fitted to vehicles of repeat offenders. The percentage of drivers who have interlocks installed is so low that the device has had little effect on the drink driving population as a whole.

In principle detection of alcohol can be achieved via odour sensors incorporated into the vehicle hardware (such as the gear shift) that can detect the presence of alcohol in perspiration. A warning can then be instigated via the navigation system, providing the driver with information on the nearest safe place to stop (e.g. a service station). The technology is still in development. For example sensors might be placed close to the driver’s face to minimise confusion with a passenger’s breath. Alternatively facial monitoring could be used although there could be some confusion with fatigue monitoring (eye blinks and closure).

Alcohol detection systems are still being developed and evaluated. As with all enforcement there are privacy issues – except where fleet managers have a no drink-driving policy in place as part of their terms and conditions of employment.

Carriage of Dangerous Goods Enforcement

The transport of dangerous goods such as chemicals and dangerous products (known as hazardous materials in the USA or “HAZMAT”) - needs to be regulated in order to prevent accidents to people, infrastructure, other transport and the environment. Different regulations are in place across the world. The United Nations Economic Commission for Europe (UNECE) has issued Recommendations - which, for roads, is elaborated in a UNECE agreement. Although not legally binding, their recommendations are widely accepted internationally. ITS can help support these regulations – for example by monitoring the position of a vehicle, so it can be located efficiently and accurately if an emergency arises. (See Enforcement)

The position of a vehicle carrying hazardous goods can be tracked continuously, either actively or passively. In both cases, Global Navigation Satellite System (GNSS) is essential to identify the vehicle’s position.

A passive tracking system stores data on the vehicle’s location and other information (such as vehicle condition or container status) which can be examined retrospectively.

An active tracking system requires data to be sent by wireless communication to a control room for monitoring in real-time. In addition to location, further dynamic information (such as status of the truck or condition of the dangerous material) can be collected by the on-board unit. Active tracking is valuable in an emergency situation and also has wider benefits. For example:

  • it allows control of the shipment along a specified (planned and authorised) route by automatically notifying dispatch and operations personnel when the vehicle deviates from the route. The monitoring centre is also able to advise the driver of a route change for any reason (such as congestion or road accident)
  • it can help prevent incidents through monitoring the condition of the vehicle and its dangerous load – an automatic alarm can be raised if abnormal conditions are detected
  • it incorporates automatic procedures for recording and logging incidents
  • emergency response teams can be informed directly of incidents and provides a facility for two way dialogue between the driver and the dispatcher

Overloading Enforcement

Overloading a heavy goods vehicle has road safety implications but is also a major factor in the deterioration of road structure of the vehicle.

Safety may be compromised if an overloaded vehicle becomes unstable when driven at the limit of its safe performance. For example, braking distance increases with greater load which may lead drivers to underestimate stopping distances. Risk of tyre failure increases as they heat up under increased load. In addition, if a load is piled high, the raised centre of gravity increases the risk of vehicle rollover. The likelihood that a driver may lose control of the vehicle is greater when the vehicle is overloaded or the load is overweight, unbalanced or shifts its position.

Damage to roads by overloaded vehicles leads to higher maintenance and repair costs and shortens the life of a road. This places an additional burden on the road owner for maintenance and reconstruction. Other road users may carry the associated costs. Overloading also shortens a truck's service life and increases its operating costs and the need for unscheduled maintenance. (See Weight Screening)

There a number of ways of monitoring overloading:

  • a vehicle inspection station whereby highway transportation personnel weigh vehicles under static state conditions
  • load-based toll station charging of vehicles based on monitoring their loadings
  • law enforcement patrols whereby personnel weigh suspicious vehicles at random at the roadside using portable weighing equipment (truck scale or weighbridge)
  • automatic axle load sensors placed in the road or on bridges

Driver Distraction enforcement

Drivers rarely “just drive”. There are many different activities a driver engages with, in parallel with controlling the vehicle and maintaining a safe course. Some are considered fairly harmless (such as listening to the radio), whilst others have a more serious impact on driver performance (such as using a mobile phone to text or make a call).

Vehicle manufacturers offer a variety of in-vehicle “infotainment” systems ranging from navigation to email in addition to driver assistance systems such as lane departure warning. All are potential sources of distraction in addition to roadside information and distractions - including large LED advertising displays, Variable Message Signs, roadside advertisements, traffic incidents and accidents on the highway. (See Driver Support)

As well as leading to positive changes in driver behaviour and safety, ITS applications for driver safety can also lead to negative outcomes. Attention overload and driver distraction are two examples. The design of an ITS application may present information that is either too frequent or too complex for the driver to process without disrupting the primary task of driving. Other applications which automate or simplify driving may lead to the driver being distracted by non-driving tasks. (See Human Factors)

Real time monitoring of driver distraction is not mature enough to be used with confidence. Some vehicle manufacturers have developed “workload managers” which regulate the volume of information presented to the driver at any one time to minimise the risk of driver distraction. For example as a driver enters a roundabout, incoming phone calls are delayed the vehicle manoeuvre is completed. This is work in progress. Sophisticated on-board measurement of driver distraction via camera technology and even the monitoring of brain-wave patterns is being investigated.



Reference sources

Soole D.W., Watson B.C., Fleiter J.J. (2013) Effects of average speed enforcement on speed compliance and crashes: a review of literature, Accident Analysis and Prevention, 54, pp 46-56.

United Nations (2007) UN Recommendations on the Transport of Dangerous Goods, Fifteenth revised edition, United Nations Publications, ISBN 978-92-1-139120-6

United Nations Economic Commission for Europe (UNECE) (2014) European Agreement concerning the International Carriage of Dangerous Goods by Road (ADR 2015), United Nations Publications, ISBN 978-92-1-139149-7,