Light rail tunnel under Auckland harbour could be best option to cut traffic, report says

Wednesday, 6 March 2019

A new assessment of options for a proposed tunnel under Auckland's Waitemata Harbour leans in favour of a light rail-only link.

The Transport Agency report says building a tunnel only for light rail would have the best downtown traffic outcomes, if combined with some form of road pricing.

The proposed route for a cross-harbour tunnel is from the North Shore's Esmonde Road to 'Spaghetti Junction'.

Adding road lanes to a future tunnel is estimated to send an extra 3,500 vehicles into the CBD each morning rush-hour, and severely congest approaches to both the tunnel and the existing harbour bridge.

The briefing for Transport Minister Phil Twyford underlines the limited further growth the 60-year-old harbour bridge can handle.

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A comparision of tunnel format options shows the impact on average speeds across Auckland, and distances travelled.

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The document does not offer any conclusions or advice on which tunnel option looks best, but lays out the impact of each - with and without road pricing - on traffic and public transport use.

A February 2018 briefing shows the planned tunnel would connect Esmonde Road, on the North Shore, with the motorways near 'Spaghetti Junction', which would leave the harbour bridge to continue serving the city centre.

New modelling in a September 2018 update, effectively rejects the 'do-nothing' option noting the road connections either side of the bridge cannot handle more vehicles in peak hours.

Weekday traffic over the bridge is forecast to rise 13-17% by 2046, creating severe congestion on and north of the bridge, as well as on the upper harbour bridge.

A tunnel carrying both light rail and road lanes would create congestion southbound, and severe congestion north of the bridge, requiring further motorway widening.

Morning peaks remain congested with both light rail, and the light rail/road options, even with road pricing.

The light rail-only option delivers slightly higher travelling speeds on roads across Auckland, than a tunnel also including roads.

'Providing a road crossing (with pricing) would result in a significant increase of about 3,500 vehicles entering the city centre in the AM peak, compared to a light rail-only crossing,' the briefing said.

'This would work against both GPS (government) and Auckland policies to reduce the number of car trips.'

Matt Lowrie, the editor of the transport-focussed website greaterauckland.org.nz said the briefing showed adding more road lanes across the harbour would be a 'waste of money'.

'I think this briefing should put the final nail in the coffin of a road crossing of any form,' wrote Lowrie in an assessment of the report.

'The fact that including a road crossing actually makes car travel around all of Auckland slower than a 'light-rail only plus road pricing' scenario is just staggering.'

The report by Brett Gliddon, NZTA's general manager of system design, said in the period up to September this year, decisions would be needed to start a business case to determine what form the tunnel should take, and then protect the proposed route.

The start of construction of a new crossing remains forecast for the late 2030s.