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What are tachographs?

A tachograph is a device mounted on a vehicle that automatically records speed and distance, along with the work performed by the driver-selected modes. Tachographs are activated automatically when the vehicle is in motion. A tachograph system consists of a sender unit mounted on the gearbox of the vehicle.

Part of the tachograph is the head of the recording medium. The tachograph head may have a digital or analog data transmission. All heavy vehicles manufactured after May 1, 2006 must be fitted with a digital tachograph. An analog recording hard disk drive head is covered with wax. Digital tachographs in trucks contain flash memory chips. Analogue tachograph head pens are used to track lines of coverage of the paper disk that rotates throughout the day.

The analog drives can also be electronically scanned and analyzed by computer, though the process of analog to digital conversion needs human expert interpretation for best results because the disc imperfections created by dust and scratch marks on the surface of the wax can be read incorrectly.

Digital tachograph data stored in the DDD files can be imported into analysis software. Truck and bus drivers are legally required to have accurate accounts of their activities. Records from previous days and weeks should be preserved and made available to transport authorities upon request.