Holidaymakers can expect a faster run to the Coromandel Peninsula before the end of summer, when the district's new gateway bridge looks likely to open several months early.

The Transport Agency has even acknowledged a "slight possibility" one of the two lanes on the replacement Kopu Bridge could open before Christmas, although it says between January and March is more likely.

That compares with a July target date on the agency's website for completion of the $47 million project, which includes building the bridge across the Waihou River and 2.5km of approach roads.

Advice of the accelerated target follows the closure for more than five hours on Thursday of the elderly one-lane bridge it will replace, after a bracket came adrift between the main structure and a swing span which opens about 60 times a year to let boats pass below.

Thames-Coromandel District Mayor Glenn Leach, who was in traffic halted by the closure, is looking forward to the earliest replacement of the 84-year-old bridge even though he accepts the agency's assurance that it remains structurally sound.

He wants it to pull out the stops for one of the new bridge's lanes to be opened before Christmas, to ease the traditional holiday-season bottleneck. "The sooner that bridge can open, the less problems we're going to have with the old girl."

Mr Leach envisages letting traffic bound for Auckland and Hamilton use the new bridge in a one-way system which would see vehicles heading in the opposite direction on the existing structure.

"If they're going to be that close come January or February, they should just think strategically a little bit and in those crucial days around Christmas they should break their arse to use the new bridge in any shape or form for northbound traffic," Mr Leach said.

Transport Agency acting regional highways manager Michelle Te Wharau said the opening date depended on how fast ground could be made to settle beneath the alignments of new approach roads.

"We can't speed that process - it has to do its thing," she said.

But she acknowledged there was a small possibility of allowing one-way traffic over the new bridge before Christmas "with the road perhaps not sealed and formed and perhaps we could have that going over metal".

"But I couldn't give any guarantees ... I don't want to raise expectations I can't deliver on."

Soft soil on each bank of the river has had to be compacted gradually during the project, on which Prime Minister John Key turned the first symbolic sod in mid-2009.

Mr Key, whose Government brought forward funds for an earlier-than-scheduled construction start, challenged lead contractor Heb Construction at the time to see if it could finish the job by this summer.

But Ms Te Wharau said the final layer of pre-load material was placed on the road alignments in May, and it would take three to five months to compact the ground to the level needed before pavement material could start being laid.