There is no typical width of a "road bed". It is in your case very likely a 60'wide roadbed, being 30' either side of the center line. All measurements are per the survey center line. It could also be 66 feet, 100 feet as common R/W. You can best visit the Court House for the County and look in the Map book for Railroads, and the original survey should be there showing the width of the line survey. The tie were 6'8" to 7' wide but there is no telling of the width of ballast or gravel. I never heard of anyone trying to measure from anything other that the center line or the near rail. You must go from the center line in my estimation. PRR