Double-decker buses are coming to the aid of Auckland's public transport, which will see the first one plying the Northern Busway next month.
Northern Express service operator Ritchies Transport expects the 88-seater vehicle to arrive by sea from Malaysia at the weekend, before being painted in Auckland Transport livery for trips to start between Albany and Britomart by mid-March.
Rival operators NZ Bus and the Howick and Eastern Buses are also involved in "infrastructure trials" with the council transport body to select other potential routes for double-deckers.
But although the newcomers are expected to have a clear run along the busway and over the harbour bridge, the Tramways Union warns of difficulties posed by overhanging trees and other obstacles including traffic lights and even building verandas on routes such as Dominion Rd and Mt Eden Rd.
Auckland Transport acknowledges some routes may prove unsuitable, but says double-deckers offer an opportunity to increase passenger capacity on others by up to 70 per cent, and are preferable to longer articulated or "bendy" buses.
Ritchies managing director Andrew Ritchie said his firm had run a fleet of double-decker coaches for tourists for more than 10 years and "we know where we can go".
It hoped to order 15 to 20 more once the pioneering vehicle had proven successful in clearing peak-time passenger loads on the busway.
"I don't think there will be any issues, but just to make sure it is all okay, it is better to just get one and then if we want to make changes [for future buses], to make those off the first one."
Mr Ritchie said the bus had been purpose-built over a European Scania chassis, and would be about 4.3m high.
Although it would not have a conductor to supervise passengers reaching the top deck, he expected the roll-out of Auckland Transport's electronic Hop card to buses from April to improve loading times.
He understood the council organisation did some tree-trimming along Fanshawe St so double-deckers could get close enough to bus stops, but not any major pruning.
Howick and Eastern general manager Sheryll Otway said her company was keen to select a main arterial route from its home base to the city before ordering several double-decker buses for delivery next year.
It wanted to reduce its "geographical footprint" with double-deckers about a metre shorter than its existing 13.5m vehicles.
It has attached a metal frame on one of its existing buses to a height of 4.2m, ready to start infrastructure trials next week, but Ms Otway does not expect any major obstacles.
NZ Bus conducted a similar trial along Mt Eden Rd this week, but has yet to disclose its findings.
One bus driver told the Herald that the exercise threw up major challenges from over-hanging trees and traffic lights.
Auckland Tramways Union president Gary Froggatt said introducing double-deckers to inner city streets would be "an absolute disaster" and some drivers had problems with single-deckers.
"We actually had a double decker bus some years ago, I think under [previous bus fleet owner] Stagecoach - it was tried out and came back all ripped along the top."
"Our standard buses are hitting trees now, never mind the double-deckers."
Mr Froggatt said Auckland Transport was taking too long to clear trees along bus routes, including in South Auckland, where one of his driver delegates was threatening to "take a chainsaw out there and fix it himself".