The weather-smashed Ashburton Bridge could reopen to light traffic by the end of the day, the NZ Transport Agency (NZTA) says.
Ashburton was effectively cut in half after the town's bridge was closed earlier on Tuesday, due to severe weather and flooding that caused it to slump.
The bridge sits on State Highway 1 and the closure meant it was impossible to travel south, with alternative routes already knocked out by flooding - a major blow to the South Island's transport network.
But after fears the bridge would remained closed for "the foreseeable future", Waka Kotahi NZTA system manager Pete Connors said there's a possibility of getting light vehicles over the bridge on Tuesday night.
"We've been monitoring the measurements today and since this morning when it moved it hasn't moved anymore so what we've got to do now is basically load test it," he told reporters in Ashburton.
"We will test it at the pier to make sure it doesn't move anymore and if it doesn't there's a possibility of getting light motor vehicles tonight. We will monitor that over the night - it will be under speed restriction and tomorrow we will test it for more heavier vehicles which will be heavier loading.
"It's not the first time this sort of thing has happened and we've just got to take our time in assessing these things to make sure it's safe for vehicular traffic."
The Ashburton District Council had said the bridge would be closed for several days at least. That assessment, however, was never made by the NZTA, Connors said.
"Waka Kotahi never said that - that came from other people who had expert opinion."
The bridge closure made it extremely difficult to get from the south to Christchurch. It's possible to get from Timaru to Christchurch via the West Coast but would take more than 13 hours to complete - compared to a usual 2.5-hour journey down SH1 via Ashburton.
Some alternative routes were expected to be open by the end of the day, Prime Minister Jacinda Ardern said earlier.
