Significant delays, or even gridlock, are predicted when traffic lights are installed to enter Auckland's $1.4 billion Waterview tunnel connection project.
The New Zealand Transport Agency has revealed that motorists will have to queue at ramp signals when the giant Northwestern and Southwestern motorway connection opens in April.
At the Waterview end, ramp signals will operate on both ramps into the tunnel, and on the longer east-bound ramp out of the tunnel. Motorists won't have to wait at lights heading west out of the tunnel.
Signals will operate at the Mt Roskill end of the tunnel, including the on-ramp at Maioro St.
Waterview is New Zealand's largest roading project costing $1.4 billion. An extra $600 million is being spent on widening the Northwestern Motorway and raising the marine causeway to cope with extra traffic heading to and from the tunnels.
Labour's Auckland issues spokesman Phil Twyford said Aucklanders were not expecting to have to queue at ramp signals on a project billed as the final piece in the Auckland motorway system.
"It could lead to really significant delays and undercut the journey time savings people have been expecting," he said.
Transport blogger Patrick Reynolds said the purpose of the western ring route was to provide free-flowing traffic but it had been badly designed and would open to gridlock.
"The reason for that is because of the failure to build parallel rapid transit. There is no busway," Reynolds said.
He claimed the ramp signals were being installed because of limitations on the ventilation system in the event of traffic coming to a standstill inside the tunnels.
But NZTA Auckland highway manager Brett Gliddon said the signals will be able to control traffic through the tunnel in both directions.
Delays caused by traffic signals will be offset by major improvements to travel times and traffic flows.
"When the Waterview connection opens, as part of the wider western ring route, it will be a significant step in transforming the way people and freight move around New Zealand and Auckland," he said.
"The western ring route will support movements around the city and Auckland's growth and help provide a better balance of traffic flows across Auckland's state highway and local road network."
Gliddon said completing the connection will allow more cars to travel on motorways, and reduce the number of cars on local roads.
"It is not a means of removing congestion altogether, especially in peak periods, which is no different to other major cities across the world."