At four in the morning in January the sky over Huron Charter Township carries the lights of planes lining up for Metro, and everything underneath them is white and unbroken. Ground Control Maintenance is out beneath that, plowing driveways and lots, cutting walkways back down to pavement, spreading salt where ice would otherwise set for the day. Storms cross this flat country with nothing to slow the wind, so a drive opened at midnight can need opening again by six. The measure of a night is simple: people get out on time and the path to the car is clear. That is the entire job, done over and over until the ground turns soft again.