He said the investigation was taking longer than expected because whatever the agency did at the Girven/Maunganui intersection, it would have to do at the intersection of State Highway 2 and State Highway 29 a short distance down the road at Te Maunga.
"One impacts on the other," he said.
Mr Gliddon said officials hoped to have nailed down a preferred option by the end of this year. The next phase was design and consenting, followed by construction. They hoped to have started construction before the completion of the $455 million Eastern Arterial around 2015-16.
The other long-awaited roading project, the $67 million Welcome Bay underpass to funnel Welcome Bay motorists directly into the Hairini causeway, was on track for construction to start towards the end of 2014.
Mr Gliddon said the preferred option was a two-lane underpass from Welcome Bay Rd built under SH29. The agency was coming to the end of the investigation phase, with design and consenting expected to take up to 18 months.
The issue of the underpass being built in isolation from widening Turret Rd and 15th Ave was not raised at yesterday's meeting.
Mayor Stuart Crosby told the Bay of Plenty Times last month that the council was in discussion with the agency on the phasing of the underpass and the widening. An important element would be the findings of a major Tauranga traffic study, now almost finished.
He said that building the underpass without the road and bridge widening would only shift the problem for morning commuters coming from Welcome Bay.
"The pinch point is clearly the bridge," the mayor said.
The council was also given a comprehensive update on the impact of Government policies in which economic growth and productivity was a high priority to help decide which of New Zealand's major roading infrastructure projects would be included in the three-year Land Transport Plan.
The agency's Waikato-Bay of Plenty director Harry Wilson said the cost to rebuild Christchurch and Canterbury's earthquake-hit roads had risen to almost $1 billion.
If the money was not raised from loans, it would take a big chunk of the $9 billion to be spent by the agency on all New Zealand's land transport requirements for the next three years. This included road maintenance, railways and the $300 million a year cost to police the country's roads.