Cellphone video shows the car in flames just before 9 a.m. It was on the Interstate 580 connector to Highway 24.
A woman and three children were inside. An off-duty firefighter stopped and pulled everyone out.
A woman who did not want her face shown told us what happened.
"I felt like, four people standing on the side of the road needed to be off that busy freeway," Good Samaritan Cynthia said. "So I pulled over and brought them into the car. I went and talked to the guys that were watching the car and by the time I had gotten them into the car, most of the car was in flames."
The car was a 1979 Volkswagen Bug that had just been restored.
One lane of the freeway was closed briefly.
No one was hurt in the incident.