The fire was reported on the right shoulder of eastbound Highway 4 just west of Alhambra Way at 2:51 p.m.
Eastbound lanes were blocked for more than an hour as firefighters responded to extinguish the fire, which damaged a number of wooden guardrail posts on the eastbound side.
Westbound traffic was disrupted for about 30 minutes as smoke billowed across the highway.
Traffic in both directions was beginning to flow again by about 4:15 p.m., Cakebread said.
The cause of the fire remains under investigation.
