Here is a RR crossing sign on Berckman St. in Plainfield just NW of the RV line. https://goo.gl/maps/5BT45 But where are the tracks it is intended to be protect? Looking at old maps I can't find any sidings at that location. The existing tracks haven't been at ground level for a century.
Take a look at the 1910 Sanborn maps for Plainfield, Sheet 4: http://library.princeton.edu/libraries/ ... field.html" onclick="window.open(this.href);return false;
It looks like the tracks are already elevated over Berckman St. There is an industrial area with sidings between the main and North Ave, on the west side of Berckman. One siding just south of North Ave. (parallel to North Ave) looks like it reaches east nearly to Berckman but does not cross it, but it is in about the right spot. Maybe it was extended after 1910.
JS
EDIT. I have access to a 1951 update I just checked. The siding now extends east across North Ave to Plainfield Lumber and Supply which occupies the region between the main and North Ave on the east side of Berckman.
Maybe historicaerials.com (which now also has old topos) would be helpful too