It rivals US 101 for traffic, but it goes through the Los Padres National Forest and the San Marcos Pass.

It starts in Los Olivos as a spur from US 101, goes through the town, and then the end of SR 246 at Santa Ynez.

It then reaches Lake Cachuma and passes through the Los Padres National Forest, and across the Cold Spring Canyon Arch Bridge, where Cold Spring Tavern is on Stagecoach Road which passes below the bridge.

It then briefly becomes four lanes and passes an offramp for SR 192 (named Foothill Road to the East and Cathedral Oaks Road to the West of SR 154), before stopping at Calle Real and a Southbound onramp to US 101 and ending at the point where State Street to the East becomes Hollister Avenue to the West.

[11] Except where prefixed with a letter, postmiles were measured on the road as it was in 1964, based on the alignment that existed at the time, and do not necessarily reflect current mileage.