Only two months ago, then Victorian Acting Premier John Thwaites was reassuring Victorians that CityLink’s Burnley Tunnel was safe even though Transurban was suing the companies that built it.

That was partly over concern about the thickness of the tunnel walls.

Today, it’s the fire risk that’s in focus. This morning, three people are dead after a crash led to an explosion and fire in Melbourne’s busy cross-city Burnley Tunnel, reports AAP.

Apparently, it’s the result of a collision between four trucks and three cars deep inside the tunnel. Hundreds of motorists were evacuated from both the Burnley and Domain tunnels shortly after 10am (AEDT).

While the details of the accident are still emerging, emergency services believe one truck swerved to avoid a broken down truck and collided with cars in the next lane, reports the ABC. The truck exploded into flames on impact. With the fire under control, the next battle for fire fighters is to control a diesel spill.

When the tunnel was built, world-leading experts assessed in great detail the fire risk — one of the biggest problems with tunnels.

The stringently enforced speed limit of 80kmh was an attempt to reduce such problems from crashes. 

To the same end, vehicles carrying placarded loads of dangerous goods or hazardous substances are prohibited in tunnels, according to CityLink’s website.

Dr Patrick Moriarty of the Melbourne University based Governance and Management of Urban Transport Research Centre says that allowing trucks through long tunnels is something of a calculated risk for tunnel operators, and certain aspects of the incident will be looked at closely by investigators. 

“I expect they will look at the loads being carried through the tunnel, at how they were secured and at the legislation on what can and cannot be carried across the tunnel,” Moriarty told Crikey.

“Some tunnels in the United States ban trucks altogether, but that’s not necessarily the answer. All factors affecting motorists need to be assessed after an incident like this, right down to the lighting and speed limits. Obviously, if you slow things down there is a lower chance of an accident. You can have a lane only for trucks. All these things will need to be canvassed.”