A tachograph has four basic symbols when recording information on trucks and truck drivers, including symbols for driving, working, available and rest. The driving symbol looks like a stylized clock or steering wheel, whereas the symbol for work is two sledgehammers crossed in an "X" pattern. The available symbol is a square with a diagonal line, and rest is a small stylized bed.
The driving symbol automatically appears on tachographs when instruments indicate the truck is moving. Drivers input the working denotation when they carry out tasks such as loading, unloading and unexpectedly waiting. The available symbol is for idle time when a driver is on duty, such as waiting for a ferry or awaiting other people to load and unload. Idle is also used if a second driver sits in the passenger seat for team drives. The rest symbol indicates breaks, sleep or rest time during daily and weekly work periods. Drivers may not perform any other transport-related work during rest times; they get 30 minutes of rest for every 6.5 hours.
These symbols are small because they need to fit into tiny spaces on analog tachographs. Digital versions do not need size restrictions, although small green screens indicate small tachograph symbols. Tachographs became required equipment in 2005 for all European trucks weighing more than 3.5 metric tonnes. These devices record speed, time, distance traveled and hours worked for the transportation industry.