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Introduction to Digital Tachographs

Information for drivers on digital tachographs, how they work and whats involved with the technology.

A Quick History lesson
When did this happen?
What is a digital tachograph?

What is it all about? - A Quick History lesson
Tachographs, or as the legislation calls them Ďrecording equipmentí, have been in use under the current European Union (EU) legislation (EU regulation 3821/85) for 16 years. The technical specification of the current tachograph is contained within Annex 1 of this regulation.

Over this time the tachograph has evolved. In the early days we had mechanical tachographs, which progressed to the early electronic units, but these were subject to interference by unscrupulous users. In order to combat this interference some amendments were made to the regulations that required diagnostic features to be incorporated into the tachograph, and for the signal cables to be armoured to prevent tampering. This takes us up to the modern electronic heads, for example VDO Siemens 1318, 1319, Stoneridge 8400 and the Motometer that we all know and love.

All of these analogue units record the driverís periods of duty on a waxed paper disc - a tachograph chart. These are not always interchangeable between the different units and are vulnerable to damage and tampering.

Following these, a new design of tachograph was introduced: called modular tachographs - VDOís 1324 and Stoneridgeís 2400. These still use charts, but are shaped similar to a standard stereo unit and have a remote speedometer fitted. The sender unit signal is also encrypted to increase the security of the system and reducing the need for some of the sealing requirements.

Note: EU regulation 561/2006 on driverís hours determines a driverís periods of driving, other work, breaks and rest, and how those periods of time are to be recorded by use of the different modes.
Why change?

The EU wanted to take advantage of technology now available in order to ensure the security of the recording of the driverís duty periods. The new system is less vulnerable to illegal acts by users to distort the data. The new system will also allow for easier and better control of driverís hours by operators and the enforcement authorities.

This will ensure that the original objectives of:

• Road safety
• Social legislation
• Providing a more even commercial playing field between operators are supported in a robust fashion.

These new generations of tachographs are also designed to allow operators to utilise the technology to enable low cost expansion to support other functions for fleet management.

When did this happen?
ALL new vehicles that require fitment of a tachograph (current exemptions still apply) first registered on or after 1st May 2006 must be fitted with a digital tachograph.
EU regulation 2135/98 allows the amendments to regulation 3821/85. There was a delay due to negotiations between member states over the technical specification of the new tachograph, but this has been agreed and was published via EU regulation 1360/2002 (commonly referred to as Annex 1B).

It should be noted that the regulation 3821/85 still exists, including Annex 1, but has been amended by this later legislation.

What is a digital tachograph?
Digital tachographs are similar in appearance to a modular analogue tachograph e.g. 1324, 2400. They come in separate parts, a vehicle unit and a speedometer - but that is where similarities end. In all other aspects this is a totally different animal.

The Vehicle Unit (VU) is located within the driverís area of the vehicle cab. It sends a signal to the speedometer / odometer unit that is located where the driver has a clear view of it. The vehicle unit still receives a signal from the vehicle (usually from the gearbox) as the analogue units do, via a cable.

digital tachographs

The VU is the brains of the system. It is able to hold data on drivers of the vehicle and their periods of driving and duty for about a 12-month period. It will also hold data relating to faults, attempts to tamper with the system, over speeding, calibration details, and when data has been accessed, for example, by VOSA staff or Police.

The VU and the motion sensor from the gearbox will be encoded as a pair and the signals from the sensor will be fully encrypted so any attempt to interfere with them will be registered and recorded in the vehicle unit. If an attempt to replace the sender unit is made, the VU will record this attempt at breaching the security of the system. [This is a greater level of security than on the current modular tachographs]

The VU will be set to Universal Time Co-ordinated (UTC) - another name for Greenwich Mean Time (GMT) - all records will be against this time. The visual display will probably be set to the local time, but this will not affect the internal time. What needs to be remembered is that the stored record will be an hour behind in British Summer Time - for example - a driver starts at 0600 (6am), the record will show 0500 (5am). There will be no difference in the winter as we are back to GMT.

Drivers, companies (operators), workshops (tachograph calibration centres) and enforcement officers (VOSA & Police) will each have smart cards according to their specific needs. These enable them to use and / or give access to the data in the VU.

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