Key transport groups say they have been left out of a Transport Workers Union safety summit.

The summit saw a range of truck drivers, academics and politicians pore over at a safety report by Macquarie University, which criticised the scrapping of the Road Safety Remuneration Tribunal (RSRT).

The RSRT was collapsed last year during a political fight in which some owner-operator businesses feared they would have to pay higher rates.

South Australian Road Transport Association president Steve Shearer says his and other transport organisations - including the National Heavy Vehicle Regulator, Australian Trucking Association and the National Road Transport Association - were not even told about the summit.

“The union only wants to work with people who agree precisely with what the union wants,” Mr Shearer told the ABC.

“It looks very much like the unions had a summit with its friends and nobody else, now that's not a credible summit.

“It wouldn't deal properly with the issues.”

The TWU said some invited transport groups could not attend.

The union claims it arranged further meetings to fill in companies that could not attend of the summit's outcomes.

The Macquarie University report said issues of tight scheduling, unpaid work and inadequate pay rates should have a tribunal to be aired in.

The research included surveys showing 80 per cent worked more than 50 hours per week.

It also highlighted pressure on owner-drivers not to refuse unsafe loads.

The current regulations allow drivers to log up to 72 driving-hours in a week, or up to 84 hours in a seven-day period if they have extra accreditation.

Mr Shearer said serious injury and fatality rates fell dramatically since the introduction of weekly limits.