Preventing Heavy Truck Roll Overs

The session involved Powerpoint presentations and talks by three pivotal people in the road transport industry and the session was chaired by Michelle Harwood, the executive director of the Tasmanian Transport Association.

Michelle represents the Tasmanian transport industry as a Member of the Tasmanian Road Safety Advisory Council, and the Tasmanian Black Spot Committee, she is a member of the RACT’S NW Regional Advisory Committee and chairs the Tasmanian Transport and Logistics Workforce Advisory Group.

In her preface to the session Michelle stated that roll overs are a leading cause of truck occupant fatalities and indicated that the speakers would cover the latest rollover statistics; how rollovers can be prevented and the contribution that can be made by electronic braking systems.

The first presentation was given by Adam Gibson, who is an engineer employed by truck insurer, NTI and who authors NTI’s Major Accident Report, in which he analyses trends in truck safety, based on NTI’s extensive claims data.

He started on a rather gloomy note, saying: “These crashes are like watching the same event over and over and over again – a B-Double lying on its side, two-thirds of the way around an off-ramp, or a concrete agitator lying on its side on the outside of a roundabout.

“What does our data tell us about these events?”

He then introduced an unfamiliar acronym into an industry that already has thousands of them: SVURO. This, Adam said, stood for Single Vehicle Untripped Roll Over.

An SVURO occurs when no other vehicle or object is involved in the roll over, and it happens when the inside tyres lift before the outside tyres start to slide. This situation is much more likely to happen to a high-centre-of-gravity vehicle like a truck, in contrast to a car that will slide first.

Adam Gibson pointed out that his discussion would involve this type of crash and that it was Important to differentiate it from one where the roll over comes later: “It’s a case of roll overs that cause crashes as distinct from crashes that cause roll overs.”

As an example of a secondary roll over he quoted the case of a driver falling asleep, followed by the truck rolling over. In that case, Adam said, you need to address why the driver fell asleep, not why the truck rolled over.

He discussed the possibility of designing a roll-over-resistant truck, but the compromises on width and load carrying ability are just too great.

“The idea of building a roll-over-resistant truck has occurred to engineers, but all that would happen is the same type of accident, but at much higher speed,” he said.

Of course, it’s not just the design of the truck that makes it more likely than a car to roll over. Adam said that some road design is “deeply unfriendly” to vehicles such as agitators: radius-tightening entry roads onto freeways, for example, but there’s not much fleet operators can do about that.

“Often a roll over occurs on a road that is familiar to the driver,” said Adam Gibson. “And that raises the question: ‘does familiarity breed contempt?’”

His discussions with drivers and fleet managers have revealed the belief among experienced drivers that ‘they’ll feel an imminent roll over through the seat of their pants’. However, Adam Gibson has real-world experience in changing cab-suspension parameters to make the truck cab ‘feel’ stable or unstable. The actual safe cornering speed was the same in all cases.

Even if that were an accurate indication of safe cornering speed, Adam stated that data shows “most roll overs occur from back to front”, so that by the time the seat-of-pants feedback happens, the rear B-Double trailer is already gone.

“ An A-Double rear trailer is even more remote,” he said.

“What the driver feels in the cab is the result of cab-suspension design, not vehicle-suspension design.

“Heavy, torsionally stiff B-coupling (fifth wheel) trailers provide some roll over feedback, but the push for lighter trailers means that that many modern trailers have almost no torsional stiffness, so there’s no feedback.”

Another factor that helps dispel the myth that experienced drivers don’t have roll overs is NTI statistics, revealing that the average SVURO accident driver age is 43 and their experience average is 10 years.

Other NTI stats show that the daily spread – the days of the week – percentage of SVURO incidents is around 17 per cent, but Tuesdays are 22 per cent!

Gibson concluded his presentation on a serious note, pointing out that in every 40th roll over incident the driver doesn’t come home.

“So we have to get that number down.”

The next presentation was given by Wade Lewis, president of the Livestock, Bulk and Rural Carriers Association. He delivered the presentation that was compiled by COO Bec Coleman, who was ill, and the emphasis was on the human factor in heavy vehicle safety.

“The aviation industry relies heavily on telematic aids and has many fewer incidents than road transport,” Wade Lewis said. “But the common factor is human error.

“Around 80 per cent of aviation accidents are down to the human factor.”

He drew on several truck accident statistic sources to conclude that 63.5 per cent of truck accidents are caused by the human factor.

“That means two out of three serious crashes are the result of driver error or another human factor,” he said.

Another surprising statistic is that 12.5 per cent of roll overs occur when articulated vehicles are tipping – and stationary.

Wade Lewis showed several dramatic videos of truck accidents, including a log truck roll over that showed a large, unsecured log moving mid-corner; a car braking to avoid a rigid truck wrongly entering a freeway, causing a semi-trailer coming behind avoiding the car and rigid truck by swerving off the road and rolling over; a long combination where the rear trailer rolled first, dragging the entire combination over and, finally, a container trailer rolling over in a roundabout.

He highlighted the particular problem with containers having ‘invisible loads’, where the container is packed by another company and its contents, load security and centre of gravity (CG) are unknown. When that’s combined with negative road camber, roll overs are all too common.

Lewis displayed a list of 48 factors that can cause a roll over and stated: "Of the 48 causes of a heavy vehicle roll over, 70 per cent are down to the human factor.”

“We can’t eliminate human error but we sure can do a better job of understanding these factors and improving road safety,” he said.

“It’s also important to recognise, and not reprimand, staff for reporting safety hazards.

“What’s needed is a ‘get it right’ approach,” said Wade Lewis.

The Livestock, Bulk and Rural Carriers Association has developed a Heavy Rollover Awareness Program that is scheduled for launch in June 2023 and will be free to access.

It was developed to reduce heavy vehicle roll over incidents by providing free on-line tools. One tool is an independent self-investigation process to analyse accidents – primary or secondary accident cause.

One example of the HVRAP toolkit is a graphic display for haulers loading different fertiliser products, showing that different densities mean changes in CG. Lighter products result in a higher CG than heavy products and create a higher roll over risk.

Rachel Michaud is a mechanical engineer and is the technical account manager for Knorr-Bremse Australia – the local division of the global brake system manufacturer. She has an MC licence and has been conducting roll over testing at the DECA facility in Shepparton and has evidence of the safety advantages of electronic brake and stability systems.

“Electronic EBS and TEBS are the platforms for ABS and roll stability control,” said Rachel Michaud. “EBS is installed on trucks and TEBS is on trailers.

“Incidentally, ‘VSF’ (vehicle stability function) is terminology used by the Australian Government and appears in ADRs 35 and 38.

“It was adopted as a generic term for the various proprietary acronyms used by different truck and trailer makers,” she said.

Australian supplier data indicates that as at 2022, around 27 per cent of trailers have TEBS and 40-50 per cent of trucks have EBS.

“Because those systems are mandated now, we expect by 2030 the numbers will be much higher,” said Rachel Michaud.

“In the case of EBS the truck is fitted with a yaw-rate sensor, steering-wheel-angle sensor and wheel-speed sensors.

“When sensor inputs indicate imminent roll over, the system removes accelerator control from the driver and applies automatic braking, to slow the vehicle.

“In the case of TEBS it’s braking-only intervention,” she said.

Rachel Michaud ran several roll over accident videos, including one where a combination vehicle rolled over, while a car drove on.

“As all of you in this room known you cannot drive trucks like you drive cars,” she said.

“However, with trucks feeling more and more like cars, it’s easy for drivers to get out of a car and into a truck and think they’re still in the same vehicle.”

Video footage of the Knorr-Bremse test rig at Shepparton was quite dramatic, with EBS/TEBS disengaged and illustrated that a cornering speed increase of only 2km/h could make the difference between on-the edge cornering and a roll over.

With EBS/TEBS enabled, the truck entered the same bend 10km/h faster than the established roll-over threshold and the mistake was corrected, enabling a safe turn.

Another video showed a lane-change manoeuvre on an icy road done without and with EBS/TBS, where the engaged vehicle had no stability issues and the disengaged one was all over the road.

Rachel Michaud pointed out that it’s important for the drivers of trucks and trailers without EBS/TEBS to be educated about cornering speed and the importance of centre of gravity height. Also, she highlighted the need for tyre pressure maintenance and smooth driving around bends.

“Surprisingly, many fleets don’t know if their trucks and trailers have EBS/TEBS fitted,” said Rachel.

“We’ve been asked to retro-fit TEBS and found that the trailer already had it.

“Retrofitting trailers with TEBS can be done relatively easily and while truck EBS is trickier.

“However, TEBS must be plugged in to work, so it’s important that drivers are told there are not just three connections – there’s now a fourth.”

Rachel Michaud said it’s critical that EBS/TEBS are kept in working condition.

“If a warning light is on, it's critical to have the problem fixed,” she said.

“Report data should be regularly downloaded, to ensure proper operation and to examine incidents such as heavy braking.”

Drivers need to be told about the importance of reporting any incidents and she quoted the example of a rear log trailer rolling over and being lifted back up by the log loader. The incident wasn’t reported, but it’s important to know why the trailer rolled in the first place.

On a final note, Rachel Michaud said that if vehicle modifications are carried out, the EBS/TEBS systems must be recalibrated and it’s the same with a change of tyre size.

Preventing Heavy Truck Roll Overs was a most worthwhile session at Trucking Australia23, which is why we’ve devoted so much space to it.