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Brake non-conformities on a downward trajectory

The number of brake non-conformities in heavy vehicles has significantly decreased in comparison to five years ago, according to new research.

The NHVR’s National Roadworthiness Survey (NRS) 2021 inspected 13,325 heavy vehicle units across 8338 heavy vehicle combinations in all Australian states and territories between May and June.

Despite a decrease against 2016 figures, brakes still remained the highest non-conforming components – reducing from 25 per cent in 2016 to 14 per cent in 2021.

As part of the NRS, data from roller brake tests (RBTs) was collected. Roller brake testing was intended to be conducted on all axles of all units, unless it was unsafe to do so. This included weather issues or practical issues such as the unit not being suitable for testing. In these instances, a visual inspection was conducted as a means of identifying defects in braking systems.

Compared to the 2016 baseline, there was a significant decrease in the number of RBTs completed (71 per cent in 2021 versus 95 per cent in 2016), with authorised officers instead opting to conduct visual inspections.

According to the NHVR’s data, this was partly due to the different timing of inspections compared to 2016. With the wetter weather we’ve been experiencing, 19 per cent of inspections were carried out in the wet compared to 13 per cent in 2016.

There were also less RBTs conducted across all vehicle types – in line with 2016, Plant/SPV were the least likely to have a RBT conducted. Similar to 2016, the number of possible tests to be conducted on plant/SPV is influenced by the location of the inspection and the availability of mobile testing units.

Examining locations where RBTs were not conducted, the incidence was much higher in WA (73 per cent) and VIC (45 per cent). Additionally, it appears RBTs were significantly less likely to occur between 8am and 1:59pm, with one in three (34 per cent) of units not undergoing the test and having a visual inspection conducted instead.

The NHVR’s report says this could be potentially be due to time pressures felt by authorised officers, who opted for the latter option.

There were several issues observed with the RBTs when conducted. There were issues with faulty tests, influenced by factors associated with vehicles as well as the brake test unit, drivers failed to follow the instructions correctly, and some operator error in recording each axle sequentially and accurately. In some cases, axles were missed, or re-tested and sufficient information was not always available by which to interpret which results were relevant. Where these types of issues were identified, the unit was not included in the analysis.

Full air brakes, which are the most common brake type, are the most likely to experience issues of non-conformity among the three main types of brakes.

Units less than six years old are the least likely to experience any braking defect (8 per cent), whereas for units manufactured over 12 years ago defects increase to 21 per cent.

The incidence of a major defect also increases with the age of the unit, with vehicles less than six years old recording defects in 2 per cent of those examined; those in the six-12 year bracket recording a 3 per cent incidence of brake non-conformities and those over 12 years old jumping to 7 per cent.

It was also found that various manufacturers experienced higher braking defects: Western Star was at 33 per cent, Freightliner at 28 per cent, Kenworth at 23 per cent, and Mack at 22 per cent.

The NRS 2021 also recorded more units with different brake types, with 107 variations compared to just 29 in 2016.

The most common brake type amongst those identified was electric followed by hydraulic and disc. In line with 2016, units with electric brake systems were more likely to experience non-conformity issues.

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