We’ve had some questions from readers wondering about the hours of carpool lanes in Sonoma County and such, so we pitched them to Caltrans spokesman Robert Haus to answer:

Why are the HOV lanes on 101 in Marin County just one direction in the morning and evening but both directions in Sonoma County?

The first segment of Marin-101 HOV lane that opened in 1974 as a bus lane. Carpools were permitted in 1976.  Traffic congestion increased in one predominate direction and it therefore required one peak operation. As traffic congestion increased in the peak commute hours in July 1998 we conducted an extensive evaluation with the concurrence of Metropolitan Transportation Commission, CHP, and Marin County officials.  Caltrans expanded the HOV hours to 5-9 a.m. in SB, and 3-7 p.m. in the NB directions. After six months of extended hours Caltrans received many complaints about those hours.  The hours were changed back to what they were selected originally but with an understanding that we will review the hours once again after the HOV gap closure project is completed or if the congestion level increased. Since the opening of the HOV gap closure in San Rafael  congestion on Marin 101 corridor is improved and there is no need at this time to change the hours.

Traffic congestion on some segments of Sonoma 101 occurs in both directions and at both peaks, however at different hours than Marin 101 corridor. Therefore, the HOV lane in the Sonoma County is for both directions. Note that once the HOV lanes in Sonoma 101 are connected to the Marin 101 for consistency we will evaluate traffic conditions to come up with the best operational hours throughout the whole corridor in both counties.

Road Warrior note: Marin’s carpool lane hours are 6:30 to 8:30 a.m. southbound and 4:30 to 7 p.m. northbound. Sonoma County’s carpool lane hours are 7 to 9 a.m. and 3 to 6:30 p.m. in both directions from Windsor south to northern Petaluma with a short gap in Rohnert Park where Highway 101 is still being widened. Based on Caltrans data, most  Bay Area carpool lanes start at 5 a.m . and go until 9 a.m. and in the afternoon start at 3 and end at 7. Most also require a minimum of two people in a vehicle but some in the East Bay require at least three.

Does Caltrans ever change the times for HOV lanes?  If so, what are some of the factors that go into that decision?

When traffic conditions warrant the change, extension of the lanes, connections to other corridors, etc.

Is there any rule or policy that says we must have an HOV lane if we are expanding an existing freeway?

Federal Highway Act, Tittle 23 authorized the U.S.s Department of Transportation to approve HOV facilities on federal aid systems to increase the capacity of movement of persons. Section 21655.5 of the California Vehicle Code and Section 149 of the Street and Highway Codes authorize the California Department of Transportation to construct preferential lanes for buses and other HOVs.

Also remember that adding HOV lanes as well as other alternatives are evaluated for each project through the environmental process that takes public input into consideration prior to selecting the preferred alternatives. In addition, all HOV lanes are constructed in accordance to the HOV lane master plan for the Bay Area prepared by the Metropolitan Transportation Commission, which was prepared after receiving input from all nine Bay Area counties.

In other words, we are authorized to build new HOV lanes when and where they will be beneficial.


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