By 3 News online staff
Traffic in central Auckland will slow by 75 percent in the next few decades if a central city rail tunnel isn't built, according to an engineering report.
Prepared by Sinclair Knight Merz, the report says by 2021 buses will be overloaded, the average speed in the city centre for cars will be halved to 8km/h, and rail network will be at capacity, reports the New Zealand Herald.
By 2041, the bus network will be "significantly over capacity" and cars will be restricted to travelling at walking speed.
It will take between 30 and 50 percent longer to commute to the central city from West and South Auckland, and 15,200 people every day will be unable to even get into the CBD because of the traffic.
Without a rail link, the report says buses will need to have two lanes going each way, and even then, it would be pushing the limits of what the network could carry.
Mayor Len Brown, who backs the proposed rail link, is yet to see the report, which also states it would be the most cost-effective plan in the long run.
It would provide a return of 78c for every dollar spent, far ahead of a bus tunnel – 28c to 36c – and a surface bus option – 34 to 50c.
Both bus options however would run into capacity problems years before a rail tunnel would, according to the report.
The Greens welcomed the report, saying it showed the Government's current policies are a "recipe for gridlock".
“The National Government is spending billions on highways that have low traffic volumes while neglecting to invest in Auckland," says transport spokesperson Julie Anne Genter.
"Projects like the billion-dollar Transmission Gully, the half billion-dollar Kapiti Expressway, and the $1.7 billion 'holiday highway' are incredibly uneconomic and will only induce more traffic heading into our cities’ CBDs, adding to congestion once they get there."
She says the Greens want the rail link built, as it will benefit not just people using public transport, but everyone in Auckland.