Traffic started flowing northbound about 3.15pm yesterday, with southbound lanes open about 10 minutes later, after the completion of demolition works to remove the bridge rubble.

The bridge collapsed during a concrete pour on August 14, injuring nine people.

An engineer's report found the formwork was not braced to stop girders moving when concrete was poured, creating excessive stress.

Roads ACT director Tony Gill said the collapse would result in a four-to-six month delay in the bridge's construction. It is now expected to be completed mid-2011, about a year earlier than the overall completion date for the Gungahlin Drive Extension project. Nino Bucci