Principal arterials provide service for principal traffic movements within the City. They serve centers of activity; intra-area travel between Lakewood and other suburban centers between larger communities, and between principal trip generators. Principal arterials serve the longest trips and carry the principal portion of trips entering and leaving the overall area. Typically they are the highest traffic volume corridors in the City. The design year ADT is generally more than 15,000 vehicles per day. They frequently carry important intra-urban and inter-city bus routes.

The spacing of principal arterials usually varies from about one mile in highly developed business areas to five miles or more in rural areas. Service to abutting land should be subordinate to the provision of travel service to principal traffic movements; this service should be incidental to the primary functional responsibility of the street. Desirably it is located on community and neighborhood boundaries or adjacent to but not through principal shopping centers, parks, and other homogeneous areas.