Auckland Transport's cost estimate for upgrading Dominion Rd has ballooned by 40 per cent to $66.3 million.
That compares with $47 million which the council body announced late in 2012, after rethinking a controversial $100 million plan which included 24-hour bus lanes along the full 5km length of the route, with extra room for cyclists as well.
Although there will now be little widening - except to extend bus-lanes along the road's southern section between the Mt Roskill shops and the Southwestern Motorway - transport planners blame the latest cost blow-out on having to buy more properties than expected and design changes to preserve parking in side streets after public consultation.
That is to compensate for lost parking on Dominion Rd at peak times, to make way for an extension of bus lanes through village centres in Mt Eden, Balmoral and Mt Roskill, communications general manager Wally Thomas said.
The new cost estimate was mentioned only in passing in a press release on Friday in which Auckland Transport announced that the upgrade would begin in September, after a joint funding agreement with the Government's Transport Agency, which will pay 53 per cent.