Digital tachograph

A digital tachograph is a device fitted to a vehicle that digitally records its speed and distance, together with the driver's activity selected from a choice of modes.

In Europe, it succeeded the analogue tachograph as a result of European Union regulation 1360/2002 that made digital tachographs mandatory for all relevant vehicles 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.

A digital tachograph system consists of a digital driver card, the tachograph head, and a sender unit mounted to the vehicle gearbox. The sender unit produces electronic pulses as the gearbox output shaft turns. These pulses are interpreted as speed data by the head.

The sender unit and head are electronically paired and the pulses from the sender to the head are encrypted, therefore deterring tampering by intercepting or replicating the pulse signal in the intermediate wiring.

As well as automatically receiving speed data, the tachograph records the driver's activity selected from a choice of modes. The 'drive mode' is activated automatically when the vehicle is in motion, and digital tachograph heads usually default to the 'other work' mode upon coming to rest. The 'rest' and 'availability' modes can be manually selected by the driver whilst stationary.

In Europe, drivers are legally required to accurately record their activities, retain the records and produce them on demand to transport authorities who are charged with enforcing regulations governing drivers' working hours. Regulation (EC) 561/2006 of the European Parliament and of the Council defines drivers hours.

There are several types of digital card, depending on the function of the card owner:

The activity information is stored in the tachograph head’s internal memory and simultaneously onto the flash memory chip contained within the digital driver card whilst it is inserted into the head.

A digital driver card is issued to an individual driver by a country's driving authority on application. In the UK this is the DVLA.

Speed information is also stored, but only on the tachograph head’s internal memory. Speed data is stored in at least 1-hertz intervals, depending on the model of tachograph head.

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