The journal box has a spring-closed cover so that lubrication can be inserted. When the lubrication is used up and not replenished, the journal gets hot—and is called a "hot box." Because hot boxes have been known to cause axle breaks, derail trains, or start trackside fires, careful attention is paid to the journals on the engine and cars by the terminal and road crews. Even modern high-speed, roller-bearing-equipped, diesel railroads are not immune to hot-boxes—they have automated detectors every 50 to 100 miles.