Calamity struck Sydneysiders on Friday after a multi-car crash on the M1 Pacific Motorway southbound closed large sections of the road to motorists.

The crash initially closed two of three southbound lanes, with traffic piled up for about six kilometres as emergency services attended the scene.

Authorities gradually opened lanes up throughout the day as the crash was cleared.

Outraged Aussies took to Facebook to vent their frustrations about the traffic jam and the hefty delays which put a stump in their day.

"Worst stretch of road for accidents every single day!!" one incensed commuter wrote.

Another added: "There needs to be an alternative route. Just drove past all the people stuck in that jam, they have no way around."

One jibed: "Gee - a contra flow (sic) that has already been paid for would have been nice. A usual 1 hour trip to work took 3.5! Think of all that CO2 bellowing into the atmosphere....."

The traffic pile-up had a knock-on effect for many travellers with one commenter noting her sister almost missed a flight.

"My sister just made her flight - they had to run to the closed gate," she wrote.

"There is always some massive peak hour accident heading towards Sydney. Trains are way too slow, don’t chance this highway heading to the airport, stay overnight at an airport hotel."

One commenter claimed the driver who allegedly caused the incident was recklessly speeding and almost crashed head on with a friend of hers.

"It was a car driving high speed heading northbound on southbound side. Almost had a head on collision with one of my mates," she wrote.

Another blamed "tailgating at 110kph" and "impatient drivers" as another pointed to "too much distraction". 

"People should learn how to drive," wrote another.

All southbound lanes are now open, however authorities have urged commuters to factor in extra travel time as heavy traffic lingers.

According to Live Traffic NSW, the incident started just after 4am on Friday.

“Southbound traffic is being diverted at the Pacific Highway off-ramp for the Old Pacific Highway and can rejoin the M1 at the Windybanks Interchange,” Live Traffic wrote earlier on Friday.

“Exercise caution, follow directions of emergency services and allow extra travel time.”

One motorist said they managed to get past the accident using the diversion.

“I got through abt (sic) 40 mins ago. Traffic barely crawling,” she wrote on Facebook.

One man was taken to hospital in critical condition after the crash as another suffered minor injuries, according to The Daily Telegraph.