KEY POINTS:
Northwestern Motorway onramp signals are being installed this year to favour users of buses and car pools and to cut the number of peak-time crashes.
But Waitakere City Council members are worried that Transit NZ's ramp signals will improve motorway flows at the expense of suburban feeder roads.
Approaches to all motorway onramps are severely congested in the morning peak and at Lincoln Rd for most of the day on Monday to Saturday, says the council.
Te Atatu Rd is already choked at peak times and delays at the onramp could worsen congestion at the Te Atatu South roundabout, which serves Te Atatu, Edmonton and Flanshaw Rds.
The council also doubts Transit's assurances that the right balance can be struck unless the 50-year-old interchanges themselves are improved.
Concern has led to a deal being struck with Transit NZ that ramp signals will be switched off should "before and after" tests show they are not helping traffic flow.
Peter McCombs, who is Transit national director of the project to have ramp signalling on all Auckland motorways, said Lincoln Rd and Te Atatu Rd interchanges had to be rebuilt. The substandard Royal Rd onramp would also be upgraded to make more merging room.
But that could not be done this year, he said, and signalling would bring interim relief to motorway flows and fuel consumption.
Cameras, sensors and police patrols will check on queue lengths.
If the queues lengthened at onramps, signals would automatically increase the discharge rate through the ramp to compensate and other nearby ramps would also be adjusted.
Mr McCombs said ramp signalling in the central motorway system had reduced peak period congestion on the Hobson St to Market Rd southbound section.
Travel speeds had improved by 10km/h and homeward evening commuter traffic is cleared 20 to 30 minutes earlier.
Waitakere City is hoping that buses and vehicles with two or more occupants will share priority lanes to be installed on Northwestern ramps.
But Transit is yet to confirm whether two or three occupants qualifies for use of the lane.
* www.transit.govt.nz
