Perth gas buses to be modified after fires

Perth's fleet of 474 natural gas-fuelled buses will be taken off the road in stages over the next 18 months so all vehicles can be modified following a series of fires.

In late 2012 and early 2013 several fires broke out on late model Mercedes-Benz compressed natural gas buses.

Fire analysis experts from the original bus supplier, local fire investigation specialists, and engineering consultants from Australia and overseas conducted an investigation into each incident.

The Public Transport Authority (PTA) said on Friday that the modifications had undergone testing and field trials, and would now be carried out on the entire fleet by Mercedes-Benz and bus body builder Volgren Australia.

The PTA has also agreed to drop legal action against the firms.

The works will happen in segments so not all the buses would be off the road at once.