There are no southbound on-ramps to the motorway at Dapto and the Illawarra Highway has now been closed at Albion Park Rail.

This shifts motorists onto the deteriorating Marshall Mount Road, or the Princes Highway into Albion Park Rail, where they then travel along Station Road and Tongarra Road.

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Alternatively, they can travel north and join the M1 Princes Motorway at Northcliffe Drive in Kembla Grange.

Dapto resident Craig Taylor said the changes had added about eight kilometres, several sets of traffic lights and 15 minutes to his trip to Albion Park, where his daughter and grandchild live.

Instead of taking the Illawarra Highway down to Albion Park, he now has to travel via Albion Park Rail because there is no on-ramp.

"I don't think it would have been that hard [to add one]," Mr Taylor said.

Vehicles trying to turn right off the highway onto Station Road often banked up, he said, impeding traffic heading straight.

Mr Taylor also feared a fatal collision would occur on Marshall Mount Road's narrow bridge with the increasing traffic.

"[The bypass] is certainly going to take a load off the traffic through Albion Park Rail, but they've done a 90 per cent job when they could have done 100 per cent," Mr Taylor said.

Judy and Ian Rimell also live in Dapto and drive to Albion Park for church.

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"The road you have to go the long way round, they're not built for the traffic," Mrs Rimell said.

She said Station Road was residential, and Marshall Mount Road was built to service those on the farms.

The condition of the roads, especially Marshall Mount Road, were concerning.

"It's not the distance of it so much as the safety," Mrs Rimell said.

She said the Dapto area had grown considerably, and only continued to expand.

Mr Rimell added that it made sense to build on-ramps at the same locations as off-ramps, and to do so after a project was completed would cost much more than it could have.

A Transport for NSW spokesperson said 65 per cent of traffic through Albion Park Rail was expected to move onto the bypass.

"This is expected to improve travel times for those travelling on the Princes Highway, with traffic modelling indicating that it would only take about one minute longer for someone travelling south from Dapto on the Princes Highway rather than on the bypass," they said.

The bypass is due for completion late this year.

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The spokesperson also said modelling had indicated that an interchange at Yallah was not required until there was a "substantial increase" in traffic.

"Transport for NSW is planning for future improvements to the M1 Princes Motorway between Figtree and Dapto. The Yallah interchange will be assessed as part of the planning for this project," they said.

The Illawarra Mercury drove from Mount Brown Road in Dapto to Hamilton Road in Albion Park, via Albion Park Rail, at the time of school pick-up on Friday.

That took more than 21 minutes; the return journey north on the bypass took about six minutes.

The Mercury reported on the lack of southbound on-ramps at Dapto in August 2019.

The interchange at Oak Flats will stop operating as a roundabout and will instead be governed by traffic lights.

Work to carry out these changes will take place this weekend, with the interchange closed from 6pm on Saturday, June 5 to 5am on Monday, June 7, weather permitting.

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