The bridge, a section of which slumped during the flooding that hit Canterbury in recent days, was closed yesterday morning, then reopened to light vehicles late last night.
It remained open until mid-morning today, then was closed again to allow further testing to determine whether it could take heavy vehicles.
The testing today involved fully-laden trucks being driven across to test its structural integrity and strength.
Waka Kotahi NZ Transport Agency advised just before 3pm that the bridge had reopened to light vehicles - generally weighing less than 3.5 tonnes - only, with a 30kmh speed limit.
The agency said it was likely to close again between 6pm and 8pm today for further stress testing of a damaged pier.
"This is needed to decide if the bridge is able to safely take trucks, until repairs are completed on the sunk pier," said Pete Connors, System Manager for Waka Kotahi/NZ Transport Agency.
He said one pier was found to have sunk by around 130 mm yesterday morning as a result of the floods. This required a full-day bridge closure for the first round of dead load testing to be organised and undertaken.
“We need two more hours of testing tonight to decide if trucks will be allowed on the bridge alongside light traffic, like cars," Connors said.
“We understand this places pressure on people to get home in time if they live on the other side of the bridge. We apologise to anyone who has to take the additional detour on local roads, or delay their journey until 8 pm to use the bridge.
“Once we have this information, we will be in a good position tomorrow to make a decision on the truck access.”
An alternative route was opened last night for heavy vehicles.
