MARIN COUNTY, Calif. — Expanding school bus service is the best bet for curbing traffic congestion in this Northern California county, according to a new report.

The Marin County Civil Grand Jury, an investigative body that monitors the performance of local government, last week released “Yellow School Bus for Traffic Congestion Relief,” which gives an overview of local traffic and transportation issues and makes recommendations to address them.

Marin County, located across the Golden Gate Strait from San Francisco, has a population of about 260,000 people and a total land area of 520 square miles. The grand jury report identifies traffic congestion as a top concern among residents, with school-related traffic being a significant factor in the overall issue. Reducing the number of cars on the road, the report says, is a more effective approach to mitigating gridlock than are other projects like widening roads or optimizing traffic signals.

The grand jury points to yellow school buses as the best way to get more single-family cars off the road and decrease school-related traffic.

“If school buses were more widely available and used, it could make a significant, positive impact on congestion,” the report says. “Increasing school bus usage seems to be our best chance at reducing school-associated traffic congestion.”

The report also provides a historical background on pupil transportation funding in California.

“School buses were the norm until the 1978 passage of Proposition 13, which rolled back property taxes and capped annual tax increases,” the grand jury notes. “As funding dried up and many yellow school bus programs were cut back, parents were compelled to drive their children to school.”

Another decline in funding from 2000 to 2015 prompted further reductions in transportation service, according to the report, and several school districts in Marin County cut their entire school bus programs. Still, some local districts continue to offer various levels of school bus transportation.

The new report from the Marin County Civil Grand Jury cites a 2015 study conducted by Marin Transit, in partnership with the Transportation Authority of Marin and the Marin County Office of Education, that also supported the expansion of yellow school bus service in the county.

However, there are hurdles to be cleared in order to boost busing. The grand jury report cites the need for secured bus parking locations, dependable funding sources, and coordinated school bell times as key challenges that would have to be addressed.

Even so, the grand jury recommends the development of a coordinated yellow school bus service, to be managed by Marin Transit, for the urbanized areas of Marin County. The goal would be to begin operations by the 2019-20 school year.

The grand jury also calls on Marin County and local municipalities to “make financial support of all [yellow school bus] programs a part of each year’s budgeting process.”

The Marin County Civil Grand Jury’s school bus report is available here.