A tachograph is a device that records a vehicle's speed over time. Usually fitted to lorries behind the speedometer, a tachograph records the lorry's speed and whether it is moving or stationary. The mechanical tachograph uses a stylus to plot a line on a moving paper disk that rotates throughout the day, where one rotation encompasses 24 hours. The marker moves further from the center the faster the vehicle is moving. However, these are vulnerable to tampering, and so are being replaced by electronic tachographs which record data on smart cards.
Tachographs are mandatory for lorries in some jurisdictions and drivers can be required to produce them on demand by transport authorities who are charged with enforcing regulations governing drivers' working hours.
Digital tachographs make tampering much more difficult by sending signals in an encrypted manner. EU regulation 1360/2002 makes digital tachographs mandatory for all vehicles described in the above section Regulations and manufactured after August 1, 2005. Digital tachographs would be required as of May 1, 2006 for all new vehicles for which EWG regulation VO(EWG)3820/85 applies, as is published in the official newsletter of the European Union L102 from April 11, 2006.