Dr Annette Beaufils said it could lead to a "life-threatening" situations.

Dr Beaufils' practice is in Helensburgh but she sees patients from Stanwell Park.

Before and after consulting hours, she sees "acute" patients - those who have just fallen ill and couldn't get an appointment.

And, because the Radio Doctor doesn't operate in the Helensburgh area, she and other local doctors do after-hours house calls as well.

Dr Beaufils feared much of this would be impossible to do during the eight-week closure of Lawrence Hargrave Drive at Stanwell Park, which starts on June 9, where a short trip between Helensburgh and Stanwell Park will change to as much as an hour each way.

"I don't know how I will be able to continue this service - doing house calls, emergency visits, the acute clinic, when I've got to factor in a one-hour trip between Helensburgh and Stanwell Park," Dr Beaufils said.

"If we're at home in Stanwell Park, how do we get to Helensburgh? At the moment my travel time between Helensburgh and Stanwell Park and back again is 10 minutes. But if we have to go the coast road that's going to be over an hour."

She said not being able to do the after-hours house calls or the acute clinic could lead to a "life-threatening" situation.

"This is going to be a hard winter, by the time we get the coronavirus and the flu and every other cough and cold around," she said.

Dr Beaufils was also concerned how ambulance and other emergency vehicles were going to cope with Lawrence Hargrave Drive closed at Stanwell Park.

"I don't see that they have given us any clear plan for emergency services," Dr Beaufils said.

"Our ambulance station is in Helensburgh - they attend to most of the emergencies in Stanwell Park."

A Transport for NSW spokesman said it was working on measures to deal with this issue.

"TfNSW has consulted with emergency services and will continue to work with them to minimise the impact of the closure," the spokesman said.

"If required during an ongoing emergency such as bushfires or flooding, emergency services will be able to travel through the work site."

The spokesman said non-emergency service vehicles would not be allowed through the work site.

"TfNSW is encouraging people to contact their healthcare and service providers and make alternate arrangements for treatment during the closure," he said.