Weighbridges

Weighbridge Type 

Some years ago NDOT developed 3 standard weighbridge specifications, as follows: 

A Grade   :   An “A” grade weighbridge installation is the description which is given to 2 weighbridge stations opposite each other on a high traffic volume roadway, each station covering a separate traffic direction.    The weighbridges are (full truck length) 22 metre scales, each comprising 4 separate weigh decks, to weigh the vehicle axle groups individually.   Each installation has a substantial truck park-off area. 

B Grade   :   One 22 metre platform scale weighbridge situated on a road route of medium traffic volume; with a smaller truck park-off area. 

C Grade   :   One 3 x 4 metre platform scale weighbridge situated on a road of relatively low traffic volume, with limited or no truck park-off area.   A 3 x 4 platform scale is capable of weighing a tridem axle group and is the minimum size scale acceptable for weighing axle groups for overload prosecutions.   The old “single bar” or single axle scales are not acceptable in court for axle group prosecutions. 

When these A, B, and C grading specifications were designed during the early 1990’s, there was also an attempt to link the weighbridge type or grade to manning hours; i.e. An A grade must be manned 24 hours per day and a C grade should be manned for more than 2 or 3 days per week.  A rigid system such as this is not preferable and can easily lead to unproductivity and a waste of resources.  Manning programmes must be flexible and cannot be dictated by the size of weighbridge. 

Most of the weighbridges as indicated in table 1 are provincial weighbridges and some weighbridges are no longer operational. The municipal weighbridges are primarily used for licensing purposes and overloading enforcement of smaller truck configurations. The highest numbers of heavy vehicles weighed were in the Western Cape, Mpumalanga, KZN and Limpopo. However, the highest percentage of vehicles overloaded above the 5% grace in comparison to the number of vehicles weighed were found to be in the provinces of the Eastern Cape with 34%, Limpopo with 13% and the North West with 9%. 

Maintaining the Standard of Weighbridges 

The Eastern Cape Provincial Department of Roads and Transport has the responsibility for ensuring that all weighbridges in the province are fully functional and accurate at all times. All weighbridges should be tested and calibrated bi-annually and maintained on a daily basis. When necessary, equipment should be upgraded to ensure that standards are maintained. 

Status Quo of weighbridges in the Eastern Cape 

There are 2 provincial weighbridges and 1 municipal weighbridge in the Eastern Cape where overloading is enforced . Although operational it is used on an adhoc basis. The 2 provincial weighbridges are namely: 

The Umtata TCC is currently not operational. It is situated on the N2, approximately 2 km to the west of Umtata, opposite the Ultra City. It has a 3 x 4m platform. 

The Kinkelbos TCC is a new facility that was completed during 2004 and is operational. It is situated approximately 40 km northeast of Port Elizabeth on the N2. It has a 3 x4m platform. This facility is equipped with a brake tester as well as a vehicle pit to examine vehicles. This weighbridge facility, according to various sources within the transport industry, monitors vehicles on an adhoc basis.  

• P.E municipal weighbridge  

Overloading control was consistently done on the Port Elizabeth municipal weighbridge from 1996 to 1999. Overloading control is still enforced in the area, but with less intensity. 

Construction and upgrading of proposed weighbridge facilities

As part of the National Overload Control Strategy developed for the national Department of Transport by the CSIR, a review of Eastern Cape provincial overload control strategies was carried out. Some of the findings were related to the proposed weighbridge sites, the proposed site according the ADTT and in relation to major corridors.  

Figure 1 Major corridors for the movement of heavy vehicles in the Eastern Cape

The proposed TCCs in the Eastern Cape in priority order, as contained in the Eastern Cape section of the National Overload Control Strategy, are shown in the table below.   

Table 1     Proposed TCCs in the Eastern Cape

Table 2     Proposed and existing TCCs prioritised in terms of ADTT

The proposed site west of East London on the R72 is the only site on a major corridor where no traffic counts were available. 

Table 3     Proposed and existing TCCs in relation to major corridors

Most of the major corridors would be adequately covered by the existing and proposed TCCs, with the exception of the R56 and the R75. 

N2 

The N2 would be covered by four TCCs of which two (Van Stadens and Umtata) would be close to where the N2 enters and leaves the Eastern Cape.   The other two (Kinkelbos and East London) would cover the central portion of the N2. 

N6 

The N6 would have a TCC where it enters the Eastern Cape at Aliwal North, one in the middle section (at Queenstown) and one where the N6 ends at East London. 

N9 

The N9 would have one TCC close to the point where it enters the Eastern Cape at Middelburg and a second TCC in the middle section (at Graaff-Reinet). 

N10 

The N10 would have one TCC close to the point where it enters the Eastern Cape at Middelburg, a second TCC in the middle section at Cradock and a third TCC where the N10 joins the N2 close to Kinkelbos.  Depending on the volume of heavy vehicles, it may be necessary to construct a satellite station at the intersection of the N2 and the N10 to monitor heavy vehicles travelling from Grahamstown on the N2 and the turning right onto the N10.  If the volumes are low, regular screening with a portable scale may be adequate.

R56 

The R56 would only be covered by one TCC at Middelburg, which is the one end of the route.  Depending on the traffic volumes it may be necessary to have another facility on the R56 and Elliot may be the appropriate location.  A TCC at Elliot would cover the R56; the R58 from Aliwal North, which is an alternative route to travel to Umtata; and the R396 which is a link between the N2 north of Umtata and the R56. 

R61 

The R61 would be covered by the existing TCC at Umtata, a second TCC at Queenstown and a third TCC at Cradock. 

R72 

The R72, which is an alternative route between East London and Port Elizabeth, would be covered by two TCCs at both ends.  At the one end it would be the proposed TCC west of East London and at the other end it is the existing TCC at Kinkelbos on the N2, a short distance after the R72 joins the N2. 

R75 

The R75 would only be covered by one TCC at Graaff-Reinet.  It is recommended that a site for a second TCC be identified in the vicinity of Despatch or Uitenhage.  This would result in the R75 being covered at both ends. 

In terms of the number of major routes covered by a TCC, the proposed facility at Middelburg would have the highest priority, as it would cover the N9, N10 and R56.  It would also cover traffic travelling on the R61 and then turning north on the N10 to travel to the Northern Cape or the Free State. 

The proposed TCCs at Cradock, East London (north), Graaff-Reinet and Queenstown would all cover two major routes.  Of these, Queenstown should have the highest priority, as it would be the only facility in the north-western part of the Eastern Cape.  It would cover the N6, which is the route from Gauteng via the Free State to East London and Umtata.  It would also cover the R61, which has recently been upgraded by SANRAL.

Proposed type of weighbridge 

Fixed weighbridges 

The types of permanent weighbridges proposed for the Eastern Cape facilities similar to what has been provided at Kinkelbos.  These facilities would primarily be equipped with an axle unit scale consisting of a single deck 3.2m wide and 4m long being capable of weighing a maximum mass of 40 000kg. 

Where the traffic volumes warrant it a multi-deck scale consisting of four individual decks with lengths of 3m, 6m, 7m and 6m respectively, giving an overall length of 22m, with a width of 3.2m should be provided.  Each deck must be capable of weighing a maximum mass of 40 000kg, giving a total weighing capacity of 160 000kg. 

A standard requirement at all TCCs should be a roof over the scale as has been provided at Kinkelbos.  This will improve the working conditions and will make it possible to do weighing in all weather conditions.

Weigh-in-motion equipment (Wim)

The provision of high-speed weigh-in-motion (HSWIM) equipment on either side of the approaches to TCCs, connected to monitors inside the vehicle of a traffic officer, is an efficient mechanism to achieve manpower and infrastructure effectiveness. This will also enable the Department to gather accurate information on traffic volumes and overloading control from which the maintenance plans can be accurately calculated and law enforcement activities co- ordinated.    

It is more appropriate on high volume roads, but can also be effective on lower volume roads for both screening and traffic data collection.  The use of HSWIM equipment will lead to less legal vehicles being weighed statically.  The total number of vehicles that has to be weighed at a TCC will therefore be less and a smaller facility may then be adequate.  The HSWIM equipment can also provide valuable traffic data that can be used to monitor trends and to schedule shifts to ensure the maximum effect.  The information can also be used by other departments, such as for long term road planning and maintenance planning.  It is therefore recommended that HSWIM equipment be provided at each TCC. 

A weigh in motion sensor being installed 

Vehicle load monitors 

Where satellite stations are not warranted, at least one set of portable dynamic scales should be supplied to each TCC.  These portable dynamic scales can be set-up next to any road where there is a suitable surface and an area to pull off and weigh trucks.  These scales cannot be used for law enforcement purposes, but are sufficiently accurate to identify vehicles that are probably overloaded with a high degree of confidence.  When screening vehicles on alternative or escape routes, a number of overloaded vehicles should be identified and then escorted in a convoy to the TCC to be weighed on the static scale for prosecution purposes. This process was effectively done by the PE traffic department on the N2 from 1996 to 1999, with the assistance of the E.Cape TMT survey team. 

Due to the fairly high accuracy of the portable dynamic scales, screening can take place at considerable distances from the TCC, as the chance of diverting vehicles that are legally loaded to the TCC is slim.  Diversion distances of up to 100km are reasonable. 

Survey being conducted via the VLM