The 194-year-old convict-built Mitchell's Causeway, a key link in the main highway connecting Sydney to western NSW, will be closed for at least three months for urgent repairs.
The Blue Mountains causeway was closed on Sunday after significant cracking and movement were detected in the road's substructure.
Further investigation has revealed that extensive testing and repairs are needed to make the section of the Great Western Highway safe for traffic.
But businesses at the bottom of Victoria Pass fear they may go under without financial assistance.
The Lolly Bug in Little Hartley has seen no through traffic since the highway closed.
"Our takings are down 75 per cent so we definitely should be compensated," Chloe Tofler told AAP.
"We're not seeing anybody, only locals who are actually coming to support us."
Beyond the economic impacts on small businesses, the return commute for some school students has blown out to nearly two hours, up from 20 minutes.
"With the price of fuel and the wear and tear on your car, it's just crazy," Ms Tofler said.
The closure of the road was unavoidable to save lives but various measures to support locals are being explored, Roads and Regional Transport Minister Jenny Aitchison told reporters on Friday.
"No one can predict the movement that has happened in the last few months," Ms Aitchison said.
"(The) significant geological movement in this site ... is not something that we've seen in the last 200 years."
Transport for NSW advises at least two weeks of specialist geotechnical testing and 3D imaging must be carried out with no passing traffic to understand the full extent of the damage.
Even under the most optimistic scenario, any remediation required to make the road safe for vehicles would take at least a further two months, the government said.
"This slope ... has been under close monitoring and has had over $20 million invested in the last couple of years," transport deputy secretary Matt Fuller said.
The causeway carries heavy trucks and other traffic down the slopes of Mount Victoria to Lithgow, the gateway to NSW's central west region.
It's the main route between Sydney and Bathurst, which is due to host an NRL fixture between the Cronulla Sharks and Penrith Panthers on Saturday night.
Trains between Bathurst and Katoomba will be free from Saturday with extra services between Bathurst and Mount Victoria from Sunday.
An alternative road route via Darling Causeway is adding about 25 minutes to crossing the Blue Mountains.
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