I was recently looking at the NTARC (NTI) safety report for 2021.
I often look at the NTARC series of reports to educate myself about Australia’s heavy-vehicle safety in Australia.
One statistic knocked me over. The proportion of large loss claims involving “roll over while tipping” is about 5 per cent.
As shown in the report extract below, this category does not capture rollover incidents caused by driver error.
The actual number of rollovers is greater than 7 per cent of NTI’s large loss claims!
The report estimates that about 1 in 400 trucks will be involved in a large-loss insurance claim in any one year. So the rate for ‘roll over while tipping’ is 5 per cent of 400, which is 1 in 8000 insured vehicles.
Just how many tip-trucks and tip trailers are there operating in Australia? A few years ago, ARTSA-i Data analysed the bodies on trucks and trailers that were registered in the NEVDIS database.
The results showed about 7.5 per cent of trailers have the term ‘tip’ in the description. For rigid trucks the percentage was about 16 per cent.
In total about 5 per cent of the registered vehicle fleet has a tipping function. So, I conclude that each year, about 1 in 400 insured trucks with a tipping function will be involved in a large-loss insurance claim involving roll over whilst discharging the load of either the truck or connected trailer.
The NTARC safety report also identifies the jurisdictions where the ‘roll over while tipping’ events occurred. An estimated 39 per cent of the incidents occurred in Western Australia and most occurred within a 50km to 350km radius around Perth, WA. Wow!
A quick Google search shows that only about 10 per cent of active mines in WA are within 350km of Perth, so this is not a mining industry problem. NTARC identified the contributing factors as:
• dense (ie heavy) and sticky loads;
• the length of tipping bodies on semi-trailers; and
• lack of torsional coupling between units due to the 50mm pin coupling on semi-trailer dolly trailers.
I think this means the semi-trailer separated from the dolly trailer during the roll over event.
Note that a dolly trailer is not roll coupled to the towing vehicle so the torsional loads cannot be passed forward. Add to that: long bodies (4-, 5- or 6-axle dog trailers or 14.6m semi-trailers); cross slope exceeding 5 degrees; over-zealous lifting of the body; moving of the vehicle with the body raised; sticky load, soft and uneven surface and high wind.
There are no stabiliser legs for tip-trailer -they are dangerous machines. Clearly the NTARC is concerned about the length and weight of loads on semi-trailer tippers.
If a dolly trailer is involved, then the incident must have occurred on a combination vehicle. Indeed, NTARC is very clear about this.
Around Perth, “these losses all involved multi-combination tippers carrying fertiliser/soil conditioners for agricultural use, predominantly lime sand.”
This safety problem seems mainly to exist in the agricultural sector.
It may not be surprising to lean that many areas within a radius of 350km of Perth are recognised as poor because of soil acidification. But there are other regions in Australia with acidic soils.
Many are in NSW and Victoria, also. Lime sand sticks so the load can be very high during tipping. I started thinking about how the trailer EBS (TEBS) system on tipping trailers might be able help a driver to assess whether it is safe to tip.
Since 2019 most new heavy trailers had to have a Vehicle Stability Control (VSC). This is an ABS with a roll stability program (as a minimum).
The roll stability program protects against roll over during cornering, not tipping. The main trailer TEBS (another name for ABS + VSC+ intelligent brake control) suppliers can now provide enhancements that help the driver avoid ‘tipping-rollover’.
For example, the TEBS contains a lateral accelerometer. An electrical output can be programmed that is true when the cross slope exceeds a pre-set value.
This can be used to halt the PTO operation.
A separate output feature can be programmed to come on if the trailer is driven off with the body raised.
TEBS unit may be able to control the air suspension (if fitted) and lower the bag height in preparation for tipping.
Occupational Health and Safety regulations require that the rollover risk while tipping be controlled. Every tip-trailer with TEBS should have these interlocks installed.
The safety features are there for the asking. It would be difficult in court to argue that you forgot to ask!
More generally, the TEBS unit can be interrogated via a trailer mounted Information Module to report the history of roll stability interventions.
For example, the Knorr Bremse Trailer Information Module (TIM) is shown below. Comparable units can be obtained from the other major suppliers Wabco and Haldex.
The TEBS information can also be downloaded to the service workshop computer via a cable connection. The TIM information screen can also show the trailer mass via a calibration involving the air suspension bag pressures.
It can also report wheel temperatures and tyre pressures on sensed wheels. I wonder how many operators are learning from their trailer EBS modules? I suspect it is only 10 per cent.
Dr Peter Hart,
ARTSA-I Life Member
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