Transit is promising to begin construction of a new bridge to replace the Coromandel's 80-year-old Kopu Bridge - but not until mid-2011.
Chief executive Rick van Barneveld made the announcement yesterday after Thames car dealer Ian Richardson raised concerns in the Herald on Monday about the safety of the one-lane bridge.
Mr Richardson, who was alarmed by information on Transit's website saying the bridge was an earthquake risk, said last night that the announcement was "a victory for common sense".
"It would be nice if they could say 'we're starting tomorrow' but it just can't happen by the time they tender and what have you," he said.
"But at least now someone has put their hand up publicly - and that's the chief executive of Transit - and said 'We're going to build the bridge'."
Transit had previously said construction of a two-lane replacement bridge would begin between 2010 and 2012, but Mr van Barneveld's announcement provided official confirmation of the timetable.
"We know how important this project is to the people of the Thames Coromandel district and other regular users of State Highway 25, and the work has been done to allow us to confidently plan for building it," Mr van Barneveld said.
Mr Richardson, who has commuted across the bridge for 18 years, had called for construction of the replacement bridge to begin as soon as possible after reading on the Transit website that the existing structure was at risk of collapse in a moderate earthquake.
But Mr van Barneveld said it was important to put the information on the website into context.
"The bridge is safe," he said.
He said although the structure did not meet today's design and construction standards, analysis had shown it was likely to withstand an earthquake of between one-in-300-year and one-in-500-year magnitude.
Bridges today were designed and constructed to withstand a one-in-2500-year earthquake.
Mr van Barneveld also sought to alleviate concerns about the Kopu Bridge by saying Transit had a robust inspection programme, and the structure was continually monitored and maintained.