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