How are the exit numbers determined?
Each exit number is determined by the number of miles it is from the beginning of the route. The numbers progress from south to north on north-south routes and from west to east on east-west routes. In the case of northbound Interstate 5, exit number 519A at the Q Street exit in Sacramento indicates that it is 519 miles north of the origin of Interstate 5 at the California-Mexico border. Interchanges spaced less than one mile apart will be assigned a suffix letter (A, B C etc). For example, Exit 519B on Interstate 5 in Sacramento is the J Street Exit and is 0.85 miles north of the Q Street Exit, but is still within the mile 519 zone. Exit numbers increase in the northerly or easterly direction and decrease in the southerly or westerly direction.
