Also, in the event of an emergency it could take as long as two hours to reopen the road.

Next year Transport for NSW is planning to close Lawrence Hargrave Drive between Stanwell Park and Bald Hill so slope stability work can be carried out.

READ MORE: LHD closure was planned for August

The plan is for two one-month closures, with the Transport for NSW preference being to close the entire road.

However, Transport for NSW has also asked for options that would allow the road to be partially opened while the work is carried out.

During the full closure, all traffic from Stanwell Park to Thirroul looking to head north, would have to travel south to the Lawrence Hargrave-M1 motorway intersection at the base of Bulli Pass.

A draft Review of Environmental Factors created for prospective tenderers concedes congestion at that intersection could become severe as the estimated 4500 vehicles that use Lawrence Hargrave Drive each day head south.

"It is expected this intersection would experience increased congestion as a result of the additional 4500 vehicles detoured via this route," the REF stated.

"This is considered a moderate impact for all residents between Thirroul and Stanwell Park."

It called on the contractor to monitor the un-signalised right turn out of Lawrence Hargrave Drive and be prepared to take action - including traffic lights - if needed.

"If excessive delays or unsafe conditions occur at this point, implement control measures such as temporary traffic signals," the REF recommended.

The report also acknowledges that the road would need to be reopened in the event of an emergency - action which will take time.

"In the event of an emergency that requires access to the proposal area, it is estimated that Lawrence Hargrave Drive could be reopened in a period of one to two hours," the report stated.

"The timing of the proposal is outside of the period of greatest bushfire risk. Therefore, this reopening period is considered acceptable."