The commuter rail line between Airport Boulevard just south of Windsor and downtown San Rafael will cost $427.9 million to complete, about $25 million more than the previous estimate three years ago, officials said.
The increase in cost reflects a lengthening of the initial operating segment as Sonoma-Marin Area Rail Transit officials seek to eventually extend the line south to Larkspur and north to Cloverdale.
SMART general manager Farhad Mansourian on Wednesday presented the first estimate of the line's cost since the rail authority board decided in 2011 to build it in phases because of the recession.
In 2008, voters in the two counties passed a quarter-percent sales tax to fund the 70-mile Larkspur-Cloverdale line and an accompanying bike path.
The original estimate was $541 million, according to SMART's July 2008 financial plan. By 2011, the estimated cost had risen to $695 million. Wednesday's report put the project's total cost at $657 million.