The railroad tracks have a perceptible zig and zag, like a line drawn with an unsteady hand, causing the SUV outfitted with rail wheels to sway as it rolls along the route that someday may carry commute cars at almost 80 mph.
The historic, but decrepit, line has been in existence for more than a century, once running from Sausalito on the south to Eureka in the north.
By spring, the Sonoma-Marin transit agency hopes to begin rebuilding the 37 miles from Railroad Square in Santa Rosa to downtown San Rafael.
"We will be taking the rail out," said Bill Gamlen, SMART'S chief engineer. "You can feel the joints. We will be replacing them with welded rail, and replacing the ties. Most are shot."
The route along the spine of Sonoma County, on a parallel track with Highway 101, hasn't had passengers looking out of picture windows for more than 50 years.
The line runs through Santa Rosa's backyard, behind homes with chain-link fences and sheds with broken windows, by homeless encampments, next to a failed housing development where weeds choke empty building sites and by industrial areas.
There are waves from bystanders at Railroad Square, now planned to be the northernmost station when trains begin running, scheduled for the fall of 2014 but likely to be delayed one or two years.
For the commute route from Santa Rosa to Novato, the tracks have been repaired, at a cost of $68 million, by the North Coast Rail Authority to run freight trains.
But a complete rebuild will be required for the comfort of passenger trains running at 79 mph, Gamlen said. "You can feel our car lumbering along. It will not work for passenger trains."
Jon Kerruish, SMART's access control manager, is driving the high-rail vehicle and honks at a man walking along the track, someone he describes as a regular.
He also slows at a newly constructed homeless encampment near Hearn Avenue, where a woman looks startled as she pulls bicycles, bedding and packs farther away from the rails.
The top of the rails have a light rust coating that is reddish-brown in color, which Kerruish said is a sign of their recent use by freight trains.
The landscape becomes more rural south of Rohnert Park, past an old depot and a warehouse in Penngrove's historic downtown, and then to open fields until the line heads into Petaluma and past its historic station.
At the Petaluma River, the car crosses a swing bridge built in 1903, an aging structure that uses a 5-horsepower electric motor, fabric belts and bevel gears to pivot slowly on a turntable that is 10 feet in diameter.
"I like this bridge a lot, it is historic," said Danny Mihelcic, a worker for Summit Signal Inc., which SMART has hired to maintain the bridge. "It was upgraded in the 1960s, electrically. And it is reliable."
Through the Petaluma marsh, the rail bed is on top of soil that has been compacted by a century of use. It will remain undisturbed.
The top layer of rock in what is called the ballast, which is the base just below the ties and rail, and it is new and jagged, which helps keep it together, but under it is the less desirable, rounded river rock from repairs made decades ago, Gamlen said.
All of the ballast, ties and rails will be replaced to bring the track up to federal standards for high-speed commute trains, which can make the Santa Rosa-San Rafael run in about 30 minutes, Gamlen said.
The marsh is also the most beautiful part of the line. The high-rail vehicle scares up egret, a young buck and doe run nearby, a flock of gulls dot a pond and an oak tree grows impossibly out of a massive boulder.
On the stretch of track from Novato to downtown San Rafael, which is not part of the freight line, the tracks are overgrown with weeds and hemmed in with berry bushes and brush.
In some places the road bed has been washed away and some bridges over creeks need replacement.
Downtown San Rafael is blocked altogether by vehicles parked illegally next to the track.
Kerruish makes a mental note to post parking signs and hire a crew to clear the brush and weeds.
Gamlen acknowledges that SMART has its work cut out for itself.
Not only does the track have to be brought up to federal standards, the agency has a series of major tasks. They include putting up warning signs
, installing a computerized system for controlling trains, building stations and finding a site for a maintenance yard.
"We are not just building a commute line, we are building a transit agency," Gamlen said.