Frontage roads force a design decision. Texas likes to run the frontage roads through the interchange ramps. California generally displaces the freeway about 20

Frontage roads force a design decision. Texas likes to run the frontage roads through the interchange ramps. California generally displaces the freeway about 200m from major surface roads to avoid running the surface street through the ramps. CA-92 at US-101 does that. When too many layers are needed, CALTRANS often goes for a tunnel underneath. See CA-92 at I-280, and SF's 19th Avenue at I-280. At US-101 and I-280 in San Francisco, a frontage road does go through the ramps. The interchange was spread out horizontally to avoid piling up all the levels.