Concerned ACTION bus drivers say going to work is "like playing Russian roulette" because overweight drivers are damaging seats, creating a risk that they could "bottom out" or collapse mid-trip.
A public interest disclosure made by two drivers last year shows that one of them had to take more than a year off work after being injured by a seat that "bottomed out" during a test run that he was directed to undertake in 2016, after raising concerns about the seat three days earlier.
"Bottoming out" means that a metal-on-metal jarring occurs at the base of the seat because of a pneumatic air-ride failure.
The public interest disclosure shows that Comcare accepted liability for the driver's lower back injury, which was described as an aggravated lumbar sprain, and that he has since returned to work.
The injured driver, who did not want to be identified, said he and a colleague had spent about four years trying to get ACTION to ban drivers who weighed more than 130kg.
Driver's seats on Canberra's public buses are built to withstand either 130kg or 150kg, and ACTION's bus driver recruitment information tells prospective drivers that they are required to weigh less than 130kg at all times.
However, the two concerned drivers, who both weigh less than 100kg, said they had never been weighed at work, or been required to inform ACTION of their weight.
They made a "conservative estimate" that dozens ACTION drivers would be heavier than the seats' load-bearing capacities, and with drivers circulating through ACTION's fleet of buses, getting behind the wheel was "like playing Russian roulette".
"Any given driver could circulate through 30 buses in a 12-month period," the injured driver said.
"It's like a virus."
The injured driver said that without a mandatory requirement for drivers to be weighed, there was no way ACTION could guarantee its seats were safe for drivers of any weight.
He said this created the potential for seats to "bottom out" or collapse.
"If a seat collapsed, a driver could lose control of the vehicle, which could be catastrophic," he said.
The Canberra Times asked Transport Canberra and City Services, which is responsible for ACTION Buses, a series of questions including whether a program was in place to monitor drivers' weights and ensure they complied with the seat manufacturer's specifications, and if so, how many drivers exceeded the safe weight limits.
Rather than answer the questions individually, the government directorate replied with a list of bullet points that it said "should address" the questions.
It said Transport Canberra was "working with other ACT government departments on systems and process for monitoring driver body weights", and that Transport Canberra made "every effort" to ensure the safety and wellbeing of drivers.
All drivers were required to undergo an annual medical assessment to confirm they were "medically fit to do their job safety".
Drivers have told The Canberra Times the assessment does not include being weighed.
Transport Canberra also said that its buses travelled about 26 million kilometres each year, and that in 2017 there were just four reported incidents of seats "bottoming out".
Driver's seats were replaced every four years, or sooner if required, and 105 seats had been replaced or refurbished so far this financial year, the directorate said.
Lawyers acting for the injured driver and his concerned colleague sent a public interest disclosure to Workplace Safety Minister Rachel Stephen-Smith in August last year, raising their safety concerns.
The ACT government solicitor responded on behalf of Transport Canberra in December, saying the issues raised did not amount to disclosable conduct under the Public Interest Disclosure Act, and that Transport Canberra had already taken a number of steps.
These included establishing its bus seat replacement and refurbishment program, and having a process in place for drivers to report issues.
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