KEY POINTS:
Transit NZ expects new traffic signals due to operate daily from today at one of Auckland's busiest motorway on-ramps to ease - not worsen - congestion on local approach roads.
It says trials of the Gillies Ave "ramp" signals for several hours at a time, over three days a week, have already improved northbound traffic speeds by 8km/h to 12km/h between there and Symonds St while reducing queues on approaches to the motorway.
That is despite a fear of the Newmarket Business Association that the signals would merely shift congestion back from the motorway to feeder roads such as Alpers St and Broadway, especially as traffic became more constricted from construction projects including a replacement motorway viaduct.
Although the signals will be switched on every day from this morning, they will operate only between 9am and 3pm until similar traffic controls can be commissioned in coming weeks on the four closest "upstream" motorway ramps - at Greenlane, Ellerslie, the Southeastern Highway and Mt Wellington.
The Gillies on-ramp carries about 21,000 vehicles a day including large streams of airport traffic, and business association general manager Cameron Brewer says the signals are likely to prove "the most problematic in the region".
"Transit's timing couldn't be worse for our shopping district," he said yesterday.
"Only a few days ago, Statistic NZ released the country's worst retail figures for 11 years and now we have another Government department putting the local traffic on a red light for the benefit of the motorway above."
But Transit travel demand project director Peter McCombs said extensive trials of the new signals showed traffic flowing faster up the on-ramp, and therefore away from Gillies Ave and contributing streets, when they were switched on.
"It enables the motorway to work more efficiently and to take more traffic away from the surrounding street network, and provide effective relief to arterials that have otherwise become clogged."
Mr McCombs said that was common to all signals Transit had commissioned so far in a $70 million project which will ultimately cover 61 on-ramps on Auckland's three main motorways.
Although 25 signals already operated on the Southern Motorway, Transit had received no complaints from councils under a memorandum of understanding requiring it to switch them off if traffic queues stretched too far down local roads.
But he said trials of the Gillies signals showed special benefits in making it considerably easier for traffic joining the motorway to change lanes at more evenly-spaced distances from other vehicles jostling to reach the Khyber Pass off-ramp about 800m north.
That had resulted in speed improvements of between eight and 12km/h between Gillies Ave and Symonds St, while also making it easier for traffic to reach the on-ramp.
SIGNALS PROJECT
* Number of signal sets: 61 to cover most on-ramps on Auckland's three main motorways.
* Cost of about $70 million includes $43 million for the signals and supporting technology including traffic sensors embedded in the motorways. The balance is going on civil works such as widening 14 of the ramps for priority lanes for heavy trucks and vehicles with two or more occupants.
* Completion date: May 2009.
