An articulated truck set alight on the N2 in Somerset West saw the highway being closed on Monday evening, City of Cape Town traffic officials confirmed.
Spokesperson Maxine Bezuidenhout said the truck had allegedly been petrol-bombed.
Fire and rescue services spokesperson Jermaine Carelse said the Volvo 440 truck was not carrying any cargo at the time of the attack.
"The driver was just a bit shaken, otherwise [there were] no injuries," he added.
The N2 inbound was closed at Onverwacht Road but was reopened shortly before 19:00 after the blaze was extinguished.
Bezuidenhout said protests had been reported in the vicinity in the early hours of Monday morning, but none had occurred at the time of the attack.