Weather delays cut to viaduct speed limit

Work on the new Newmarket Viaduct has already begun. Photo / Glenn Jeffrey

Speed restrictions to be imposed on drivers using Newmarket Viaduct while a replacement structure is built next to it have been delayed a week because of wet weather.

Rain on Sunday and Monday nights meant Transport Agency contractors were unable to mark narrower lanes on the viaduct's southbound carriageway, needed to make space for barrier screens on the outer lip of the 690m structure.

As those are the only nights of the week when traffic on one of the country's busiest motorway sections is light enough to allow a full closure, the agency has postponed the operation until next Sunday, weather permitting.

Because the three southbound lanes will be narrowed from 3.5m to 3.1m, the agency plans to reduce the maximum speed on that carriageway from 100km/h to 70km/h.

The reduced limit will also allow for visual distractions while a 140m lifting gantry is erected above the traffic to build a $215 million replacement viaduct.

Traffic on the northbound carriageway, which will retain 3.5m-wide lanes for now, will be restricted to 80km/h in line with the motorway speed limit between the viaduct and the Onewa Rd offramp in North Shore City.