Peter Airey, an engineer with more than 40 years experience, said Transport Minister Dean Nalder had asked his company for advice on the idea of tunnelling under roads such as Canning Highway and Scarborough Beach Road.
Mr Airey said creating freeways and tunnels underneath main roads would be a more cost-effective option than road widening.
“When I had a talk with the minister, he was interested in aspects of Canning Highway and Stirling,” he said.
“We had a look at the cost of doing this for Canning Highway and our assessment was that putting a four-lane freeway underneath would cost about $150 million, which is only a few million more than the repossession of the land and the moving of services, such as sewage and electrics.
“This is not political, this is just technically a reasonable alternative instead of widening the road.”
Opposition transport spokeswoman Rita Saffioti labelled the idea “out there” and “not realistic”.
“Frankly it’s never going to happen, it’s too expensive,” she said. “We need practical solutions that are achievable over the next five to 10 years.”
Mr Airey said the technology was available.
“There are a number of patents registered in Western Australia that are focused around this technology and how this could deliver up to twice the traffic at less than half of the cost of normal road-widening options,” he said.
“Local traffic can still circulate, but if you want to go to Scarborough or West Coast Highway from somewhere like Main Street, the business of going through all those sets of traffic lights and intersections is a pain and very slow.”
Mr Nalder would not comment specifically on the idea of tunnels but said the government was developing the Perth Transport Plan for 3.5 million people.
“In the past decade, Western Australia’s population has grown by more than half a million people, more than the entire population of Tasmania,” he said. “Once the Perth Transport Plan for 3.5 million people is finalised, the government will release it and it will address many of the transport challenges we face.”