Matters were made worse when a truck jack-knifed due to the oil spill, authorities said.
The accident involved an articulated vehicle and three cars, which left two people slightly injured, said provincial Traffic Chief Kenny Africa.
The busy highway was closed off to traffic at 3.07pm, and traffic was diverted from the N2 outgoing at Raapenberg Road, onto the M5 South-bound.
Road users on all main roads leaving town were left to sit in traffic for at least two hours.
One bus commuter said she had to pray for her bladder after the bus took 30 minutes to “crawl at a snail’s pace” from the terminus to the nearby Good Hope Centre.
City of Cape Town Traffic Head, Richard Coleman, said one shoulder lane on the N2 was opened just before 5pm.
“Only the right shoulder opened on the N2 outbound and the closures [were] expected to remain in place for another two hours,” said Coleman.
Africa sent a WhatsApp update just after 6pm to say the truck had been removed and the spill was to have been cleared by 6.30pm.
“Truck will take another 30 minutes to clear the oil and diesel spill, but the N2 remains closed,” he says.
By 7pm yesterday, traffic was still gridlocked out of the city.