Caltrans on Thursday opened the new northbound carpool lane on Highway 101 in Novato.

The new lane runs from Highway 37 to Atherton Avenue. Last month, Caltrans opened a new segment of the southbound carpool lane in about the same area of Novato.

Construction of  both segments of the carpool lane, which are the fourth lane in each direction, cost a total of $49.3 million and took about a year to do.

Marin County’s carpool-lane hours are 6:30 to 8:30 a.m. southbound and 4:30 to 7 p.m. northbound.

Next up for the highway’s widening in Marin is extending the southbound carpool lane from Atherton Avenue to Novato Creek and the northbound lane from Atherton Avenue to a bit south of the Redwood Landfill dump. Crews are scheduled to begin work later this year with completion by fall 2013.

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