Almost every episode features scenes of Nash and Joe driving through the streets of San Francisco, seemingly never having to stop for red lights. If you look closely in the background, as they drive past major intersections, you can often see actual San Francisco motorcycle cops holding back traffic to allow the scene to be shot, thereby enabling Nash to drive through the City without ever stopping.
Although Nash Bridges' car is referred to as a 1971 Plymouth Barracuda (the grille/headlamp, mirrors, and tail light configuration is that of a 1971 Plymouth Barracuda.) The actual cars used were 5 Total, (4) 1970 Plymouth Barracudas and (1) 1973 Coupe (used as FX Car)converted to look like 1971 Hemi Cuda Convertibles. None actually had a Hemi motor, but rather 318-440 motors. 1 stick and 4 automatics.
Nash Bridges 1971 Plymouth Barracuda "Hemicuda" was at the time and has been the most expensive production vehicle on the classic muscle car market. The vehicle was worth at least $450-700k in the 1990s and is now $2-3 million USD for the 15 known models.
The San Francisco Police Department (nor any police department) would allow its employees to drive such an expensive vehicle for routine police work.