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Auckland's historic Grafton Bridge will re-open on Monday, although it will be reserved mainly for buses during most daylight hours.

Cars and trucks will be restricted to night crossings.

The 99-year-old bridge, which has had $6.9 million of structural strengthening during a 12-month closure, will operate as the central component of Auckland City's $43 million busway between Britomart and Newmarket.

But although Link buses will use it from next week, after an official ceremony and public open day to be hosted on Sunday by Auckland City Mayor John Banks, other bus services will be phased in over several months.

That is mainly because KiwiRail is building a new bridge over the western railway line in Park Rd, at the Newmarket end of the Central Connector busway, meaning a continuing tight squeeze for traffic until the end of next month.

Other bus services will be added progressively between then and early next year, towards an expected daily use of the busway by 65,000 passengers, who are promised faster trips by avoiding much of the congestion on Khyber Pass Rd.

Although the Park Rd bridge construction is on schedule, as part of the western line and Newmarket rail upgrades, the busway project has caused sequencing problems by being completed three months earlier than expected.

It has included widening Symonds St and Park Rd to provide 24-hour bus lanes, and improving footpaths with new paving and canopies for the convenience of pedestrians and bus passengers.

City council transport committee chairman Ken Baguley said yesterday that Symonds St had been turned into a "fantastic looking" boulevard, befitting its importance as a university precinct and a transit corridor.

He was pleased to see students already making use of a new pedestrian crossing mid-way between the Wellesley St and Alfred St intersections, rather than bunching up on street corners or dashing dangerously across the road in front of heavy traffic.

Newmarket Business Association chief executive Cameron Brewer said that although his organisation was disappointed private vehicles would not be able to use Grafton Bridge during week days, it appreciated what the council was trying to achieve.

"The Central Connector will be a great piece of 21st century public transport infrastructure for Auckland."

Grafton Bridge will remain closed to cars and trucks between 7am and 7pm each week-day, leaving its two lanes - one in each direction - free for buses, emergency vehicles, motorcycles and bicycles.

Mr Baguley's transport committee asked staff to review that operating scheme, but decided to stick with it after it won support from affected groups including the Auckland District Health Board and the Grafton Residents' Association.

Council officers also warned that changing the bridge-use scheme risked triggering a reconsideration by the Transport Agency and the Auckland Regional Transport Authority of their combined $34 million contribution to the project.