The Mother Road book, used as part of the inspiration for Cars.
The Mother Road is used as a metaphor to refer to the historic Route 66. The cars of Radiator Springs are seen using it as part of their culture and believes.
Route 66: The Mother Road is also a book, wrote by Michael Wallis, who also is Sheriff's voice actor. In this book, Wallis tells about Route 66's history and attractions. He collaborated with Cars' creators such as voice actor and guide. He has led the troupe on a beautiful journey around the USA, to visit all the Route 66.