A 50:50 joint venture (JV) between engineer and environmental consultant SSI and structural and civil engineering firm Asch Consulting Engineers has started with a contract for the South African National Roads Agency Limited (Sanral) in Limpopo province.

The JV is responsible for the detail design and supervision of three high-technology traffic control centres.

The contract is valued at about R170-million.

The scope of the project includes two traffic control centres, including three weighbridges and holding areas, serving both directions of the Limpopo N1 and the R101, and a satellite traffic control centre without a holding bay on the intersection of the N11 and R101.

SSI transport sector group manager Pieter Van Niekerk says there was a delay on the start of the project, as the initial procure- ment tenders received were insufficient, and additional electronics had to be incorporated. “This changed the scope of the work and it had to re- tender. The project started about three months later than envisaged; however, all work is now up and running,” he says.

Further, at the N11 site there was concern when an old burial site was identified on a verge of one of the sites. Department of Environmental Affair’s requirements stopped work for a while, and changes had to be made to accommodate the burial site, after which work continued.

Van Niekerk says the project is currently about three or four months behind schedule and the project is still in its infancy, with completion set for between April and May 2009.

The contracts for the electronics are currently being released and the earthworks, the layworks and the trenching for the cabling have started.

SSI project manager Vuyiso Msipa says the facilities use weigh-in-motion technology beneath the surface of the road to alert road officials to possible payload infringements. By weighing the force of each axle, officials can determine whether the vehicle is within statutory limits, which impose a total vehicle weight, a maximum weight within an axle span limit and an individual axle limit. The first two limits ensure the safety of bridges, while the third one protects the road surface.

Weight Scanning

As a vehicle approaches the N1 and R101 traffic control centres, the registration plate will be scanned and a digital image of the vehicle captured. After a vehicle drives over the weigh-in-motion sensors in a screener lane, its weight will be captured and added to the record. If a payload violation is indicated, the automated system will control the traffic lights and booms, directing the truck to the static scale area. Here it will be weighed again and its registration and image recaptured and correlated with the existing record. If there is a weight infringement, the system directs the vehicle to a holding area where its load can be repacked for better load distribution over all the axles and the vehicle released back onto the highway. If it is found to be overloaded, the transport operator will have to send another vehicle to carry the excess goods, and the payload is reduced to within legal limits.

If the payload is in violation of the legal limit, the vehicle will have to undergo a roadworthy test to determine whether it is roadworthy in its overloaded state. Depending on the severity of the findings, the vehicle may not be allowed back onto the road until it is repaired on site, or towed to a repair facility. The overloading and roadworthy transgressions will be logged onto the system, and then have to be corrected by the truck operator before the vehicle can be released.

The satellite traffic control centre on the N11 will employ weigh-in-motion sensors to identify potentially overloaded vehicles. These vehicles will then be fitted with electronic tracking tags and then directed to the N1 facility for static weighing.


The electronic systems were designed by specialist consulting company Techso, and are among a new generation of high- technology controls for traffic control centres. All the com- ponents of the system, the surveillance, tracking, weigh-in-motion, access control, roadworthy testing, the static scales and vehicle identification equipment, and the vehicle control through the booms and traffic lights, are fully integrated and automated, reducing operator involvement and eliminating the possibility of any interference with the data.

All incoming data is captured on a central processing system that collates information from the different subsystems. This creates a comprehensive database of vehicle loading, and overloading information for the authority and enables remote access to the information. The ability to gain access to and analyse information and statistics from such facilities, spread across a broad geographical spectrum, allow the authority to observe and control overloading on its road network while helping to develop a regional control strategy. All this allows Sanral to manage its infrastructure more efficiently. The vehicle testing facility also improves the sustainability of the system by tackling the issue of road safety through the testing and enforcement of vehicle roadworthiness.

The electronics and technology used on this project, compared with those traditionally used, are smaller and a lot less intrusive. Van Niekerk comments that this the only way that a proactive institution can protect its infrastructure. The deterioration of South African roads is primarily caused by overloading of trucks, and if this can be controlled, then the electronic weighing equipment is a good investment.

The system will be linked to the Department of Transport’s National Traffic Information System (eNaTIS) database for checking vehicle and driver credentials. eNaTIS is South Africa’s official register for all vehicle, driving licence, con- travention and accident data.