Anyone who has traveled over the mountain of late, even under escort, would have witnessed first hand the number of landslips along the road following the recent big wet weather event experienced by the region.

Likewise, especially over the past week, motorists would have noticed the strange drilling machines, which have also been in use on Moss Vale Road.

A Transport for NSW spokesperson said the investigations involved drilling of the road corridor to determine sub-surface material layers and foundation conditions of the supporting road embankment.

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"This information will assist Transport to determine the potential extent of asset damage and inform the design development for long-term repair works," the spokesperson said.

"These investigations have informed plans for early work that will enable us to remove some impacts to the road and restore access under a single lane closure with a stop/slow arrangement over a shorter road length."

Early work at slip sites will include removal of at-risk material from slopes, maintenance of rock fall fences, further clean-up of slip debris and adjustments to temporary concrete barriers.

Teams will also carry out maintenance work including clearing drains, repairing guardrail, replacing signs and trimming vegetation.

Meanwhile, motorists are reminded that Moss Vale Road over Cambewarra Mountain is closed for three nights this week to allow specialist maintenance work.

Once completed, this work will mean the needed escort over the mountain due to roadslips can be removed.

Traffic over Cambewarra Mountain has been reduced to a single lane and by escort only for more than a month after a number of landslips, following the widespread wet weather in February and March.

Moss Vale Road will be closed in both directions between Barfield Road and Kangaroo Valley Road for three nights between 8pm and 4am from Monday to Wednesday, May 9-11, weather permitting.

The closure will allow for natural disaster recovery and maintenance work to be undertaken.

The road will be closed to all traffic during this time and the current escort arrangement will not be in operation during the work.

Light vehicles will be detoured via Kangaroo Valley Road, adding around 15 minutes to travel time.

Vehicles longer than 7.5 metres or heavier than 12 tonnes should delay travel as there is no alternative route for these vehicles during the closure.

From Thursday, May 12 once the work is completed, access on Cambewarra Mountain will be restored under single lane closures, reduced speed limits of 40 km/h and alternating stop/slow traffic control.

Motorists should plan for delays of up to 10 minutes.

This will be instead of the current escorted travel, leaving the Cambewarra side of the mountain to Kangaroo Valley on the hour (ie 10am, 11am) and returning from Kangaroo Valley to Nowra on the half-hour (ie 10.30am, 11.30am).

Motorists are advised to drive to the conditions and follow the directions of signs and traffic control.

Access for all heavy and light vehicles to the Southern Highlands remains via the Princes Highway and Picton Road, adding 90 minutes to journey times.

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