Complex equation making it nearly impossible to put road barriers on Harbour Bridge

The state government has no plans to install a road barrier or other safety mechanism on the Sydney Harbour Bridge because of the need to adjust lanes for traffic movement.

On Thursday afternoon, two people died when a car travelling north crossed into oncoming southbound traffic, hitting a car before that car hit a bus. Another man and a pregnant woman were taken to hospital.

The situation on Thursday following the crash that left two people dead.Credit: Janie Barrett

Despite road safety being “the number one priority”, Transport Minister Jo Haylen said on Friday that lanes needed to be changed for traffic management.

“There are contraflow arrangements in place across the Warringah Freeway on the Sydney Harbour Bridge that [are] important to manage traffic flows,” she said. “That’s where we move traffic across different lanes across different times of the day. Sydneysiders would be aware that this is important to manage traffic congestion.”

Why is it so hard to install barriers to separate oncoming traffic on the Sydney Harbour Bridge?

The possible barrier

“Separation [of lanes] is absolutely the ideal,” said Geoffrey Clifton, a senior lecturer in transport and logistics management at the University of Sydney. This could be done by installing concrete barriers that separate cars travelling in opposite directions.

But with heavier citybound traffic in the morning, and the reverse in the afternoon, authorities switch the direction of the centre lanes of the bridge. That means a barrier would need to be moveable. Such systems, called road zippers, exist on Victoria and Military roads already, but they’re very expensive.

And there’s a more fundamental problem: there’s no room.

Built with only six lanes

The Sydney Harbour Bridge was built in 1932 with only six lanes of traffic. Now there are eight.

The first cars, trains and bikes cross the Sydney Harbour Bridge in 1932, with no lane markings. Credit: Mitchell Library, State Library of New South Wales

Designer John Bradfield planned the structure with two railway tracks on each side: trains travelling on the bridge’s western side would serve the North Shore line, while those on the east would be part of a never-to-eventuate Northern Beaches rail line. When that line was ditched, trams moved across the bridge, before they too were removed in 1958.

But fitting in so many cars on the bridge means narrow lanes: those in the middle of it are among the state’s narrowest, some just 2.92 metres wide. That leaves transport planners with little flexibility to insert barriers between the lanes.

“A zipper means they would have to be narrowed a little further than that,” Clifton said.

Transport officials investigated adding a zipper to the bridge in 2015 but decided against it after finding they would need to remove one lane from the bridge, reducing its capacity by 15 per cent.

“The Sydney Harbour Bridge has daily traffic volumes of around 160,000 and delays on that roadway can flow on to the entire system, as was experienced on Thursday,” a Transport for NSW spokesperson said.

“Security personnel, a network of cameras and response vehicles operate 24 hours a day to clear crashes, detect and repair road faults and help motorists and other Bridge users in distress.”

In 2022, Roads Minister John Graham, then the opposition roads spokesperson, said he supported the government considering options to improve road safety on the bridge, including a zipper. His office did not respond to a request for comment on Friday.

Clifton said: “It sounds very callous, but we have to balance getting people to work as quickly as possible, versus safety, versus everything else the government needs to do.”

“Transport planners have to make that decision every day. There is a value of life that’s been used to say, ‘If we make this change, we’ll save this many lives, but at this cost.’ That’s money that could be put into the health system that saves lives as well.”

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