A new $220 million Auckland link road designed to take the pressure off State Highway 1 is having the opposite effect, forcing transport bosses to install traffic lights to ease congestion.

Ramp signals will be erected to give traffic travelling south along SH1 a chance against motorists muscling their way on to the road from the Southwestern Motorway at Manukau.

The signals are expected to be running within three months, at a point that was originally intended to be a seamless connection.

To make matters worse, the Transport Agency says a longer-term plan to widen SH1 southbound from Manurewa to Papakura has yet to gain a funding allocation in its 10-year highways programme.

The Southwestern Motorway - part of the 48km Western Ring Route between Albany and Manukau - has been promoted as necessary to reduce Auckland's reliance - and subsequent congestion - on SH1 and the Harbour Bridge.

Transport Agency highways manager Tommy Parker said it always took time for traffic to settle down around new road links, but he hoped the ramp signals and altered road markings would balance flows.

He acknowledged that a proposal to widen SH1 south from Manurewa was not on any funding schedules for the next 10 years, but said it could always be brought forward if necessary.

Despite the reported delays, he said the new connection - which bypasses 12 sets of traffic lights along the old southwestern route via Wiri Station Rd - was offering drivers shorter trips at most times of day.

He expected the ramp signals to be installed within three months, and a new series of road markings and signs on SH1 to be ready before the end of this month.

"These measures will ease the bottleneck where the two motorways connect and significantly improve driving conditions," he said.

Mr Parker acknowledged that the agency's initial preference had been for motorists using the western ring route to be able to get free of Auckland without encountering any traffic lights.

"Ramp signals are best on on-ramps rather than motorway-to-motorway ramps," he said.

"When traffic is going at speed there are risks when it joins the back of the queue, so we try to avoid them, but I think that given the circumstances we had to make a pragmatic decision. The ramp signals will allow us to control the merge."