SMART is spending $12 million on its train crossings to qualify them as quiet zones, where approaching trains may be exempted from blowing their horns.
It is up to the counties and individual cities, however, to weigh the safety factors and apply for to state and federal regulators for quiet zone designation.
"It is a balancing act," said Farhad Mansourian, general manager of the Sonoma-Marin Area Rail Transit District. "If you are living next to the track, do you want the horn because it is the most effective safety measure? The gates come down and the lights flash and the bells ring, but there are always people who think they can beat the train."
Sonoma County Public Works Director Phillip Demery said it is also an issue of liability.
"It is not foolproof," Demery said. "If there is ever an accident and it is proven the operator didn't hit the train horn, the rail company takes the stance that they are indemnified against any accident or fatality. The city or county has to bear the risk."
The rail line will be shared by SMART and Northwestern Pacific Railroad Co. freight trains.
In usual railroad operations, commute and freight train operators are required to sound the horn 15 to 20 seconds before reaching a crossing, with a pattern of two long blasts, a short blast and a final long blast.
The required decibel level is 96 to 110, loud enough to be heard but below ear-shattering.
SMART is overhauling the train crossings as it rebuilds the track between Guerneville Road in Santa Rosa and downtown San Rafael for commute trains. Service is scheduled to begin in late 2015 or early 2016.
As part of the work, SMART is spending $12 million for such additional "quiet zone" measures as special crossing gates and traffic islands that are intended to keep motorists from being able to drive onto the tracks.
Only the cities and counties, however, have the authority to apply to the state Public Utilities Commission and the Federal Railroad Administration for quiet zone status.