A new average speed over distance camera system will go live in Cape Town in the coming weeks – an intervention which the city said will compel motorists to slow down.

The City of Cape Town has installed an average speed over distance (ASOD) system on Nelson Mandela Boulevard in its latest attempt to address speeding and promote road safety.

The installation of the system was approved by the City’s Camera Review Committee as it was considered to be the best measure to address speeding along this particular road.

The cameras will become operational later this month – October 2014 – and will measure the speed of all vehicles travelling inbound and outbound between the bottom of Nelson Mandela Boulevard and the N2 and M3.

The system consists of three sets of cameras that will cover all of the incoming and outgoing lanes.

The first set is on the footbridge over Nelson Mandela Boulevard in the vicinity of District Six; the second set is on the Main Road bridge over Settlers Way; and the third set is on the footbridge at Mostert’s Mill on the M3.

The installation of these systems is provided for in the City’s contract with Syntell, which means there is no capital cost to the City.

Below is an illustration of what a typical ASOD System looks like and how it works.

System basics

A typical Average Speed Over Distance system comprises of a set of cameras at one end on a stretch of road (start point) and another set of cameras further down that same stretch of road (end point).

The average speed would then be calculated by using the distance between the two points and the time taken to cover that distance.

In the case of ASOD systems, the distance between the start point and the end point for that section of road has to be certified by an accredited institution and this distance is used when the system does the calculation.

Vehicles that travel the defined distance in a time less than that specified results in the generation of an offence record which is then presented to the prosecuting authority.

ASOD cameras

An ASOD system uses specialised cameras which record every vehicle that passes. These are referred to as Automatic Number Plate Recognition (ANPR) cameras.

There is also a GPS receiver connected to each camera to accurately relay the time.

In each unit there are two cameras (BW ANPR and Colour Overview), both synced to each other. Each unit is equipped with an on-board computer that processes the information passed onto it by the cameras, using proprietary software.

The camera uses the number plate of a vehicle as its trigger. Once a number plate has been detected, one camera takes a snapshot of the number plate and the other takes an overview snapshot of the vehicle. At this point, the exact time that the vehicle passed the camera is also captured.

The system then combines the two images, location coordinates, date, and timestamp into one encrypted file.

This process takes place in the cameras at each end of that section of road.

It should be noted that a vehicle passing any of the cameras at the start point does not have to pass the camera in that same lane at the end point for the matching process to occur. The vehicle can travel between any two cameras on that section for matching to occur.

Sending the data for processing

The encrypted files from the cameras are transferred to a secure server, using wireless P2P technology, where the data sets are matched live.

The matching takes place to verify whether or not a vehicle passed the start and stop point on that section.

The server has proprietary software installed that handles the processing of all the encrypted files.

The encrypted files are received for each section and, using this information, the system will determine whether or not an offence has occurred.

A fine is generated for vehicles that travel the distance in a shorter time than allowed by the speed limit.

All of these processes up to the infringement being generated are done automatically by the system. An officer has to inspect every infringement before the Section 341 notice is printed.

Not the first average speed cameras

The City of Cape Town introduced a similar system on the M5 between the Kromboom Road and the Ottery Road bridges a few years ago.

On that stretch of road, the system has generated just over 14,500 fines since August 2012.