The clerk keeps track of all the cars coming in the yard...As each train comes in,he will list the cars by hand as they do at Rigby and he will make up the switch listfor the yard crews and enter into the computer as to what track they will be on.
The train master or Yard master,who is incharge of the yard itself assigns the work weather it be switching or locals to the crews, assigns the engine,make sure they have the right paper work,i.e. speed summaries and wheel report for road and locals,assigns the track for incomming trains, calls for transportation if needed for crews, co-ordinates between North Billerica and other assignments, call for track or engine maintainers etc...The yard is his territory...and when all goes wrong be it his fault or not, gets chewed out...He has alot of responsibility....Most locations on the main line have automatic car readers that will list the trains, but they don't always work.