Voters in Marin and other Bay Area counties might be asked to add up to $3 to bridge tolls to fund a host of transportation projects in the region, including completion of the Novato Narrows freeway widening project.

The Metropolitan Transportation Commission on Wednesday began discussing plans to seek state legislation to allow it to ask voters for a toll increase in 2018. Those talks could start as soon as next month. The ballot measure would be tallied regionally among all nine Bay Area counties and would need a simple majority to pass.

If Regional Measure 3 gets on the ballot and is approved, a $1 toll increase would raise $127 million annually for transportation projects in Marin, Alameda, Contra Costa, Napa, San Mateo, Santa Clara, Sonoma, Solano and San Francisco counties. A $2 increase would generate $254 million a year, and a $3 hike $381 million annually.

A toll increase amount has not been determined.

“The collective thought was to do something big enough to make a difference,” said Randy Rentschler, director of legislation and public affairs for the Metropolitan Transportation Commission, after his presentation to the commission at a workshop in San Francisco.

If approved, the increase would occur on the seven state-operated bridges in the region, including the Richmond-San Rafael Bridge. The current toll is $5, with Bay Bridge tolls rising and falling during peak and off-peak hours. The Golden Gate Bridge is run independently of the state and would not be subject to the toll ballot measure.

A spending plan still needs to be developed, but Dianne Steinhauser, executive director of the Transportation Authority of Marin, hoped dollars could be included for a trio of large county projects.

“This could help us finish the Novato Narrows widening project and build a connector from the Richmond-San Rafael Bridge to Highway 101,” she said. “That latter would take congestion off of Sir Francis Drake.”

While various segments of the Narrows have been widened in the two counties over the past five years, more funding is needed to finish work in the 17-mile corridor between Highway 37 in Novato and the Old Redwood Highway interchange in north Petaluma. The overall project has a price tag of $743 million and it is about $250 million short.

Marin County transportation officials have also been eyeing a connector from Highway 101 to Interstate 580 near the Richmond-San Rafael Bridge. Presently drivers need to use Sir Francis Drake to get to I-580 from Highway 101 and vice-versa.

The lack of a direct freeway-to-freeway connector from northbound Highway 101 to I-580 helps vex an already troublesome northbound traffic pattern in Marin during the evening commute.

“We could all benefit from that connector if it was built,” said Steinhauser, who attended Wednesday’s workshop.

A new transit center in downtown San Rafael could also be on a list of big-ticket items for Marin, she said. New Sonoma-Marin Area Rail Transit commuter train service running through the existing hub by as soon as 2018 will necessitate the center being moved within five years. A new transit center could include housing, something the Metropolitan Transportation Commission is keen on seeing built with new transportation projects.

Two previous toll measures have been passed by voters. In 1988, Regional Measure 1 established a uniform $1 base toll on state-owned toll bridges in the Bay Area. That resulted in a $117 million rehabilitation of the Richmond-San Rafael Bridge. Regional Measure 2 was passed in 2004 and added $1 to existing tolls. The SMART commuter rail project has gleaned $82 million from that fund.