Santa Cruz county California has a triple rack on the front of every bus. They do get used heavily - certain routes at certain times of the day are often at capacity. They've had racks for a long time - perhaps 20 years ago they had a four position rack on the back of the buses used on a few routes.

Santa Clara county California has double racks on probably every bus. They get used sporadically - but many of the routes run quite frequently. The light rail and heavy rail also both allow bikes.