Some figures for consideration re the AKL harbour bridge cyclelane costs. According to TNZ's own info hidden away on their web site, the average construction cost for recent major bridge projects nationwide is approx. $1,500/m2. Assume the bridge is 1,200m long and is widened 1m each side (to add to the space created on the existing bridge deck) and you arrive at just under $4 millon. The rate/m2 is for new bridge construction and may be high? for just widening work, but this is a tricky site so it may be appropriate.
Obviously this is just ball park stuff but is closer to the $3-5 milion figure rather than the $30 to 40 million TNZ has estimated.
The same TNZ info has the average cost increase from tender at 17%.
The entire brand new Upper Harbour bridge and casueway at Greenhithe cost $36 million. Hard to see how a bit of widening on the other harbour bridge can cost the same.