The Brief Carpool lane hours are changing on part of Highway 101 in Marin and Sonoma County. Carpool lane hours changingWhat we know:Sometime in late February, Caltrans will shorten and unify the HOV commute lane signs along the 52 miles of Highway 101 from Mill Valley in Marin County and Windsor in Sonoma County. I think we could do with shorter commute hours back to hours it used to be was good. You know, now I think the commute hours are a little overboard," said commuter Javiar Jacinto. Compressing commute hours actually encourages commuters to use carpooling, ride-sharing, transit, and SMART Train.