Cars commonly catch on fire from electrical issues, overheating, malfunctioning or negeglected maintenance on transfer cases or transmissions. We get a car fire at least once a month. This average increases during the summer and
does not count semitrucks/trailer fires.
I'm a firefighter for my county that includes ~ 30mi of interstate along a national corridor. DOT has estimated 11,000 vehicles pass through our county each day on this corridor.