More than a quarter of all truck drivers say they are under pressure to drive at high speeds and a similar share are pressured into carrying overweight loads, according to a survey of almost 1000 drivers.
The survey, commissioned by the Transport Workers' Union, also revealed that one in two drivers say they work more than 12 hours a day.
The survey was commissioned as part of the union's campaign to reduce pressure on drivers and trucking companies from major clients, including Coles and Woolworths.
The surveyed drivers said pressure caused a significant minority to at least consider breaking the law.
About 30 per cent said they felt pressure to exceed safe driving hours, while almost 10 per cent said they felt pressure to use stimulants to fight fatigue.
Michael Kaine, assistant national secretary of the TWU, said the survey was another piece of evidence that pressure from Coles in particular was compelling unsafe driving practices.
"They're the aggressors in terms of their supply chain," Mr Kaine said.
