CMJ - Stage 1 Frequently Asked Questions

Why was much of the work carried out during night time?

Work was carried out at night to ensure that motorists could use the motorway without undue delays and major traffic congestions. In order to get access to certain work areas lanes must be closed off. This was not feasible during the daytime when traffic flows could not cope with lane closures. Some work, therefore, had to be carried out at night when traffic can cope with a reduced number of lanes.

The construction team had the difficult task of balancing competing objectives:

• To reduce impact on traffic (i.e. work is best carried out at night time when the traffic volume is at its lowest)
• To avoid disruption to residents (i.e. minimise noisy work at night time)
• To complete the works as swiftly as possible

Why were on- and off-ramps frequently closed overnight?

The work could often only be carried out along a very narrow corridor that was only accessible through the closure of ramps. Because ramp closures during the day would have a significant impact on traffic flows, this was best done at night.

The construction team always aimed to find the best possible solutions and was totally committed to completing the job as safely and quickly as possible.

See also above.

What was done to minimise construction noise at night?

The construction team used a range of techniques to minimise noise during night time construction activities. Noise reduction measures included:

• Screens to buffer work areas
• Acoustically lined shells which fit directly over work areas to contain the noise
• Silencer boxes for equipment such as generators
• Mufflers for small tools

In addition, the team was also careful in their selection of work practices and methodologies. While noise minimisation was of prime importance, it was not always possible to eliminate all noise. In cases where noise could not be eliminated, activities were programmed to take place as early in the night as possible.

Specially designed acoustically lined shells help contain construction noise during night works

Why were there screens throughout the project area?

Much of the construction work was carried out behind screens - out of sight for motorists. This means that distraction to drivers was kept at a minimum, which significantly contributed to safety for motorists and construction workers alike.

Why was the lane layout changing all the time?

Work was carried out in a series of stages to keep the existing number of lanes open during the day and to minimise disruption to motorists. A staged construction programme meant that construction work affected different areas at different times. Each time the construction activities shifted to a new stage, traffic lanes were adjusted to allow space for the next work area.

Why did the barriers and retaining walls have artwork on them?

Interesting urban design features have proved a welcome addition to the 'hardware' that is normally associated with roading infrastructure. Embossed patterns on retaining walls, and the iconic outline of Rangitoto on motorway barriers, are examples of the visual enhancement. The project team has developed the design features as a result of Transit New Zealand's "Urban Design Guidelines" for the three Central Motorway Improvement projects.

Rangitoto Barriers

Why are the piers on the port ramps to/from the Northwestern Motorway such an interesting shape?

Widening the bridge with conventional piers would have impacted on the height clearance below due to the requirement for very deep beams. To maintain overhead clearance, the new lane on the bridge had to be designed to 'hang' from special outrigger-type piers which have shallower beams. The shape of the piers is the result of extremely tight geometric (road alignment) constraints involved in the bridge widening.

Bridge piers under construction