California Code, Streets and Highways Code - SHC § 145

The department is authorized to lay out and construct local service roads on and along any state highway where there is particular danger to the traveling public of collision due to vehicles entering the highway from the side thereof and to divide and separate any service road from the main thoroughfare by raised curbs or dividing sections or by other appropriate devices.

It is unlawful for any person to drive any vehicle into the main thoroughfare from any service road except through an opening in the dividing curb or dividing section or dividing line.

Any person who violates any provision of this section is guilty of a misdemeanor.