Motorway ration plan raises fear of backlog

Plans to ration scarce space on Auckland's motorways with traffic lights at every on-ramp have raised fear among city leaders that backlogs of vehicles may choke their streets.

Transit New Zealand promises close collaboration with local councils in drawing up design specifications to ensure a fair allocation of space along the entire motorway network, and to manage any flow-on effects on suburban roads.

Multinational teams of consultants will complete a "traffic demand management" investigation for the Southern Motorway by March 31, and for the Northern and Northwestern motorways three months later.

They will be required to assess ways of linking "ramp-metering" controls to information systems to help motorists plan their journeys better, even to the point of reconsidering whether they need to set out in the first place.

Roadway sensors will feed traffic information to lights at on-ramps, and to motorists through electronic signs, radio bulletins, cellphone text-messages and a website.

But North Shore Mayor George Wood fears longer delays for motorists queuing to join the flow of traffic crawling south to the Harbour Bridge, and believes projects such as the Northern Busway and studies into road pricing or tolling should be undertaken first.

Auckland City planners also want assurances from Transit that the burden will not fall unduly on drivers trying to squeeze on to motorways from central suburbs, clogging up feeder streets, while those from further away enjoy relatively clear runs.

Manukau City Council's transport committee is also wary of impacts on its streets, after mixed results from a ramp meter trial at Mangere Bridge, where drivers already queue at traffic lights to join the Southwestern Motorway at peak times.

Transit's travel demand project director, Peter McCombs, emphasised yesterday that his agency wanted a "complete management system" for the motorway network to make travel times less erratic and trips easier to plan.

Asked about concerns that controlling on-ramps may push more people to live at motorway extremities, contrary to anti-sprawl objectives of Auckland's regional growth strategy, he said Transit was keen to manage all traffic movements.

Mr McCombs acknowledged this could include using variable speed limits to slow motorway traffic in mid-stream, allowing more room for motorists to join the network from on-ramps along the way.

The scheme may ultimately involve tracking every vehicle from the time it joins a motorway to when it leaves, although he said information would be encrypted so number-plate details could only be used for traffic management.

Mr Wood said Transit's proposals needed a huge amount of consultation with communities because of a risk of skewing the motorway network at the expense of thousands of commuters using the North Shore's main on-ramps.

He was particularly concerned about the 50 per cent of southbound Harbour Bridge traffic joining the Northern Motorway at Onewa Rd or Esmonde Rd.

"The motorway is working at saturation capacity at the moment and rearranging or putting in measures right now won't change the speed of traffic."

Mr Wood said the only real way of coaxing car drivers onto public transport was to bring in some form of road pricing to discourage peak-time motoring, but he suspected the Government was dragging the chain on the eve of an election year.

Auckland City transport spokesman Garson Bell said his council would support anything that increased traffic efficiency, but would be concerned if motorway rationing meant drivers chose to stick to arterial roads earmarked for rapid bus transport.

Mr McCombs said the aim of controlling on-ramps was to prevent the breakdown of mainstream traffic flows, which were hard to reverse once past a critical point.

HOW IT WORKS

Sensors every 500m along the motorway check the traffic.

If it gets too heavy, they activate traffic lights on motorway on-ramps.

Information from the sensors can also be sent to electronic signs, radio bulletins, cellphone text-messages and a website to help motorists plan their journeys.