By RICK COLLINS
The Patriot Ledger

The last time a commuter train rolled down the Greenbush corridor was July 1, 1959.
That means Saturday’s test run will be the first opportunity for many South Shore residents to see a train rolling down those tracks.

A full-sized train, consisting of a diesel locomotive and several passenger cars, leaves South Station in Boston on Saturday morning for the 17.7-mile trip through neighborhoods, business districts and woodlands to Scituate.

The trip is the MBTA’s first major progress check on the $503 million rail project. Among other things, the test will check clearances, such as how the station platforms line up with train doors.

The train will reach a maximum speed of 10 mph and will stop before all 26 grade crossings.

There are to be no passengers on the test train, just a handful of rail officials monitoring the run and a couple of members of the media, including a Patriot Ledger reporter and photographer. A report on the trip as well as photos, will be posted on The Patriot Ledger’s Web site, patriotledger.com, on Sunday.

The Patriot Ledger was given an exclusive preview of the trip earlier this week in a ride with project officials in an SUV, modified to ride the rails. Video footage from the ride can be seen at patriotledger.com.

As some project supporters promised, the line passes through several impressive vistas, including the Fore River basin, Sanctuary Pond in Cohasset and marshlands in Scituate.

At one point the SUV stopped to allow a couple of turkeys to cross the tracks. A nearby Tom could be heard gobbling in the thick underbrush nearby; construction workers in the area described it as “huge.”

Underscoring concerns loudly voiced by project opponents, the line also runs close to a number of homes and businesses.

A neighborhood view near Green Street in Weymouth.

Along South Street in Hingham, the back corner of one home is located less than 15 feet from the tracks. Project officials say the corner is located three-quarters of an inch on the rail right-of-way.

Today’s test run is the only one of its kind expected in the near future. A more formal testing phase is expected to begin early this summer but will consist largely of a pair of back-to-back locomotives.

Project officials have scheduled a longer testing phase for the Greenbush line than other new commuter lines because of the introduction of quadrant gates at five intersections and a more complicated signaling system.

Whereas standard crossing gates consist of an arm blocking each traveling lane - and perhaps a short arm blocking sidewalks - quadrant gates feature four arms to prevent cars from dodging around the gates.

It is the first time these types of gates have been used anywhere on an MBTA line. One difference in the signaling system is that special sensors let train engineers know earlier if a vehicle has become stuck between the gates.

The Greenbush communities pushed for the quadrant gates because access to homes and businesses at some locations would have been blocked by 40-foot-long median strips. The median strips are required under federal railroad safety regulations because the towns also lobbied to prohibit train operators from blowing their whistles along the length of the line.

Whistles will be blown, however, during the testing period, as the rail’s signaling system and other safety measures are still unfinished.

The MBTA will also employ flagmen at all grade crossings to make sure traffic has stopped while the train crosses intersections.

While work crews are installing security fencing along the length of the line, project officials said they will place a priority on homes with small children, if asked by parents.

Rick Collins may be reached at rcollins@ledger.com.

In the Idlewell neighborhood in Weymouth, a worker installs an 8- foot security fence.