Digital tachograph

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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 [1] 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 tachograph is a device fitted to a vehicle that automatically records its speed and distance, together with the driver's activity selected from a choice of modes. The drive mode is activated automatically when the vehicle is in motion, and modern 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.

European Union Economic and political union of European states

The European Union (EU) is a political and economic union of 28 member states that are located primarily in Europe. Its members have a combined area of 4,475,757 km2 (1,728,099 sq mi) and an estimated total population of about 513 million. The EU has developed an internal single market through a standardised system of laws that apply in all member states in those matters, and only those matters, where members have agreed to act as one. EU policies aim to ensure the free movement of people, goods, services and capital within the internal market, enact legislation in justice and home affairs and maintain common policies on trade, agriculture, fisheries and regional development. For travel within the Schengen Area, passport controls have been abolished. A monetary union was established in 1999 and came into full force in 2002 and is composed of 19 EU member states which use the euro currency.

Digital tachograph system

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 [2] defines drivers hours.

Drivers' working hours is the commonly used term for regulations that govern the activities of the drivers of commercial goods vehicles and passenger carrying vehicles. In the United States, they are known as hours of service.

Digital tachograph head models

Digital card types

German driver card Fahrerkarte VS.jpg
German driver card

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

Data storage

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.

Flash memory Electronic non-volatile computer storage device

Flash memory is an electronic (solid-state) non-volatile computer memory storage medium that can be electrically erased and reprogrammed. The two main types of flash memory are named after the NAND and NOR logic gates. The individual flash memory cells, consisting of floating-gate MOSFETs, exhibit internal characteristics similar to those of the corresponding gates.

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.

Hertz SI unit for frequency

The hertz (symbol: Hz) is the derived unit of frequency in the International System of Units (SI) and is defined as one cycle per second. It is named after Heinrich Rudolf Hertz, the first person to provide conclusive proof of the existence of electromagnetic waves. Hertz are commonly expressed in multiples: kilohertz (103 Hz, kHz), megahertz (106 Hz, MHz), gigahertz (109 Hz, GHz), terahertz (1012 Hz, THz), petahertz (1015 Hz, PHz), exahertz (1018 Hz, EHz), and zettahertz (1021 Hz, ZHz).

When either memory bank is full, the oldest data is automatically overwritten with the current data. Design specifications prevent data being altered or deleted, therefore ensuring the integrity of the data for subsequent analysis and presentation in a court case.

Data can be locked in the tachograph head by using a company card. This ensures that the data cannot be retrieved by another company should the vehicle subsequently change ownership, or in the case or lease or hire vehicles that are used by many companies during their life. All data can still be retrieved by use of a control card or a workshop card.

Data is stored as a .ddd file that can be imported into tachograph analysis software.

Comparison with the analogue system

Advantages of digital tachographs

The digital data stored by the tachograph system can be analysed by computer and infringements automatically identified.

Digital data is encrypted and cannot be altered or deleted by the driver once stored on the card or in the head.

Information is more explicitly defined in digital form and is less likely to be misinterpreted. When an analogue chart is visually analysed, a margin of error is present, dependent on the quality of the recording and the skill level of the analyst.

Disadvantages of digital tachographs

Without a digital card reader, computer and analysis software, the data can be more difficult to interpret as it is not visually represented as the analogue chart is, and requires mathematical calculations to decipher the information from its presented format. Some Renault branded tachograph heads can produce printed information in a graphical format, similar in appearance to the activity trace on an analogue tachograph chart.

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  1. Smith, John (2016-09-22). "Tachograph". Mobility and Transport - European Commission. Retrieved 2019-09-23.
  2. Regulation (EC) No 561/2006 of the European Parliament and of the Council of March 15, 2006 on the harmonisation of certain social legislation relating to road transport and amending Council Regulations (EEC) No 3821/85 and (EC) No 2135/98 and repealing Council Regulation (EEC) No 3820/85