Four in the morning at Wellington, the first Orange Line train still an hour off and the parking aprons one unbroken drift. Crystal Bright is already out in it — plow down, driveways opened, walkways shoveled to the pavement, ice knocked back with de-icer before the day's freeze can set it. Snow removal in Medford means narrow driveways, cars parked close, and storms that come in off the harbor wetter and heavier than the forecast promised. The measure of a night like that is simple: at seven, people leave on time and never think about it once. That is the whole job, and it is a good one.