Loving tributes for 25-year-old high school teacher Melissa Bond flowed on Tuesday after her students, colleagues and friends woke to the shattering news of her death on Appin Road where her car and a truck had collided.

The tributes on Facebook included one from Gabrielle Dillon who posted her lament about "being woken up to the most dreading news that such an amazing [woman] had been taken so early".

"Miss Bond you had such a strong relationship with everyone from JT [John Therry Catholic High School in Rosemeadow] and no one can grasp the fact that such a beautiful [woman] like you had to be taken so early," the tribute said.

"You built such a strong relationship with everyone; someone who wasn't a teacher but a friend, it just doesn't feel real. Rip you beautiful [woman], you will forever hold such a strong part of our hearts.]"

The teacher is the latest driver to die on Appin Road, which once had a warning sign displaying the road's increasing death toll.

Ms Bond's Holden Cruz and a refrigerated truck collided about two kilometres south of Copperfield Road in Sydney's south after 5pm on Monday. She died at the scene.

The 45-year-old truck driver was taken to Liverpool Hospital where he was treated for back and neck pain. The Metropolitan Crash Investigation Unit is examining the circumstances of the crash.

Students from the school have posted loving tributes to the teacher on social media, making special comments about her smile, kindness and humour.

Director of Schools, Peter Turner said the John Therry Catholic High School community was mourning the loss of "an outstanding young woman".

He said the community had been deeply shocked and were heartbroken by the sudden and tragic death of Ms Bond.

"Melissa, a much loved and popular teacher at the school was travelling home at the end of the school day yesterday when she was involved in a motor vehicle accident on Appin Road at approximately 5.30pm," Mr Turner said.

"As a member of the PDHPE team and the year co-ordinator for year 9 students, Melissa was a dedicated and outstanding young teacher and role model, highly respected by her principal, colleagues and students.

"The wider Catholic community deeply mourns the loss of a fine young woman, a wonderful and passionate teacher who cared most about her students, their learning and their wellbeing."

Being woken up to the most dreading news that such an amazing women had been taken so early, miss bond you had such a...Posted by Gabrielle Dillon on Monday, March 21, 2016

Campbelltown Labor MP Greg Warren said Ms Bond's death "is another tragic and sad loss of life which would have to be one of the most, if not the most, dangerous roads in NSW".

"There have been more than 40 lives lost in 20 years," he said.

"This road is unforgiving. If you drift, the margin of error is so small that, within a meter, you can hit a tree."

Mr Warren said he met NSW Roads Minister Duncan Gay on Tuesday morning and the minister said he would provide safety upgrades to the road.

"There has been too much talk and not a lot of action so far," Mr Warren said.

Campbelltown mayor Paul Hawker said he would send his condolences to the teacher's family and school.

A sign once stood along the dangerous stretch of Appin Road warning motorists to drive carefully along what it described as an "accident zone".

Freight trucks are among the thousands of vehicles that travel each day along the road between the Illawarra and suburbs around Campbelltown.

The single carriageway mostly forms one lane in each direction, with some sections providing a second lane for overtaking.

The road extends across the Campbelltown, Wollondilly and Wollongong local government areas.

Large residential properties between Rosemeadow and Appin, the Inghams Chicken Farm, recently developed Appin Valley, Appin Township, Appin Colliery and West Cliff Colliery are among those that line the road. Between Appin and Bulli, the road is mostly surrounded by bushland.

Two bridges cross the southern section of Appin Road over the Georges River and Loddon Creek, where many serious accidents occur.

Earlier this year, Mr Gay said speed and fatigue were the "key killers" on Appin Road.

"No matter how much work we do, unless people take personal responsibility, sadly we could see more tragedies occur," Mr Gay said.

Between 2000 and 2015, more than half the fatal crashes on the road were linked to excessive speed.

The speed limit on Appin Road from the Appin township to the Princes Highway was reduced by 10km/h to 90km/h in February last year and traffic police regularly patrol the road.

Keira MP Ryan Park has previously said driver behaviour contributed to fatalities, but the road itself was also a problem.

"No doubt driver error is a problem, but that road is very unforgiving so there's not a lot of area where you can get yourself out of a difficult situation," he said.

"If someone makes a mistake there is not a lot of shoulder room, there are not a lot of dual carriageway sections, not a lot of it is separated by median barriers.

"That becomes problematic particularly because it is used by people travelling and commuting in the early hours of the morning or late at night."