Mass management 'positive' but faults remain

Governments look to on-board mass management, but study reveals technology exposed to tampering and inaccuracy

By Brad Gardner

Work is underway to develop another truck monitoring device, as governments look to an on-board mass management scheme despite its faults.

Transport Certification Australia—the body responsible for developing the controversial Intelligent Access Program (IAP)—has been tasked to come up with guidelines and procedures governing a mass management system by early next year.

A seven-month trial in 2008 tested the accuracy of twelve on-board mass management units from eight suppliers, with the TCA saying the units recorded an average accuracy rate within 500kg.

But while saying "the overall results were positive", problems remain in protecting on-board units from tampering and reducing the error rate among vehicle combinations.

According to the findings from the trial, a mass management unit connected to a truck and dog combination failed to register the correct weight by more than a tonne, while a unit connected to a B-double overweighed the vehicle by close to a tonne.

Furthermore, "measurements on tri-axle groups had a larger variation on tandem-axle groups", according to the trial’s findings, which show an error rate for tri-axle vehicles ranging from a tonne to 300kg.

The report revealed the ease with which drivers can manipulate the technology regardless of whether it runs on a vehicle with a load cell or an air pressure transducer (APT).

"Although load cell based systems provide more stable OBM (on-board mass management) readings, their resistance to tampering events still need to be examined," the TCA says.

During the trial, a wooden block was inserted into the gap left in the truck by a load cell installation.

"This created an extra point to share the vehicle weight in addition to load cells," the report says.

"On an 18 tonne vehicle, 1,650kg was unreported by the load cells in this tamper test."

The report goes on to say that a driver can achieve greater weight saving by inserting more blocks, adding that there is "no obvious way to detect this event except by physical inspection".

Drivers operating a truck with an APT were also able to alter on-board mass management readings by blocking the air supply from air bag suspension.

The report says an APT relies on access to air pressure from air bag suspensions, leading the TCA report significant irregularities in a vehicle’s weight.

"The most significant error occurred on an axle group was more than 11 tonnes below the weighbridge reading, while some systems reported similar measurements before and after the ball valve was closed," the report says.

Despite the issues, TCA General Manager of Development Dr Charles Karl says the study shows anti-tamper hardware can be developed.

Following the release of the report, TCA Chief Executive Chris Koniditsiotis labelled the study as an example of using technology to benefit the trucking sector.

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