ROADBLOCK: Traffic sweeps around the River Rd-Wairere Dr roundabout, which will soon undergo a major transformation.

Employees are being urged to work from home, stagger their starts, or carpool as the next stage of road building in the city's north threatens months of early starts and long waits.

Tens of thousands of motorists look likely to be stopped in their tracks during construction of a mammoth new intersection at the junction of Hamilton's River Rd and Wairere Dr.

More than 35,000 vehicles converge on the roundabout each day, and Hamilton City Council and contractors are finalising how they will deliver the project with maximum speed and minimal disruption.

However, big delays at three daily peaks appear inevitable.

Northeastern residents should leave home earlier, work from home or share cars to avoid peak-hour logjams expected at what is the latest major upgrade of the city's roads.

Transport managers are calling on employers to be flexible as construction of the huge new intersection sitting astride a renowned peak-hour chokepoint starts within weeks.

At present, the city's northeastern transport network struggles to handle peak traffic, when vehicles heading from the north to the CBD and south of the river clog roads, and in the evening as they head back to northeastern suburbs.

Four-laning Wairere Dr, including the River Rd chokepoint and river crossing, at a cost of $7 million, is aimed at freeing up one of the city's busiest roading bottlenecks.

The works are expected to be more disruptive than recent works at the Wairere Dr and Pukete Rd intersection.

Those works taught city council transport managers lessons they hope will limit the chaos as they start on the next junction.

Upgrading the roundabout to a full four-lane intersection with signals is expected to take months, and could yet involve staggered closures to River Rd from the south and north to all but buses, pedestrians and cyclists to get the job done quicker.

City development manager Andrew Parsons said a detailed work programme for the intersection, where construction could start by the end of July, was two weeks away.

Alternative routes for the intersection, which has major traffic flows in all directions at peaks, are limited and generally unattractive, and Mr Parsons said the key for motorists would be to avoid the daily "tidal" peaks from 8-8.30am, 3-3.30pm and 5-5.30pm.

"The River Rd site is much more constrained physically than at Pukete, so there's a number of challenges there for us, and we will be appealing to the public to help us by using public transport, or staggering work hours, but there's going to be challenges."

Regional council public transport operations manager Edwin Swaris said the Orbiter and Flagstaff buses may be rerouted and passengers can expect "unavoidable" delays.

While the overall intersection was expected to take up to eight months, Mr Parsons said works within the intersection causing "significant" congestion would not.

"Eight months of traffic parked up on the road is not the intention at all," he said.

Daytime works were unavoidable despite the clash with traffic peaks as it would be "inherently unfair" on neighbouring residential areas to work at night, Mr Parsons said.

"It may be we have some extended work hours, but as soon as you start going late at night, with families with small children, it's just not fair or reasonable."