What are Diagram Discs and Analog Tachographs?

Diagram discs are circular paper charts specifically designed for use in older analogue tachographs. These devices are installed in commercial vehicles, such as lorries and buses, to automatically record crucial driving data. Each disc, typically 12.3 cm in diameter, provides a physical record of the vehicle's speed, distance covered, and the driver's various activity periods, including driving time, work, availability, and rest. Introduced for commercial transport, these mechanical recording devices and their discs have been mandatory in many parts of Europe, including Germany, for decades, with requirements for their fitment dating back to the 1950s for specific vehicle categories.

How Commercial Drivers Use Diagram Discs

For every shift, a professional driver must correctly fill out and manage a diagram disc. The process involves:

• Pre-Drive Entries: Before starting, the driver must manually write their personal details, the vehicle's registration number, the date, the starting location, and the current odometer reading on the designated fields of the disc.
• Insertion: The disc is then carefully inserted into the analogue tachograph, ensuring it is correctly aligned with the current time mark and the excentric guiding ring.
• Activity Selection: Drivers use a time group selector switch on the tachograph to indicate their current activity. Common symbols include a steering wheel (driving), crossed hammers (other work, e.g., loading/unloading, cleaning), a square with a diagonal line (availability, e.g., waiting, co-driving), and a bed (rest periods).
• Data Recording: As the vehicle moves, the tachograph's styluses automatically trace lines onto the rotating disc, recording speed and distance. The driver's manual selections for activity periods are also recorded, often as different line thicknesses or patterns.
• Two-Driver Operation: In cases of multi-driver operation, separate discs are used for each driver, and they must be correctly exchanged in the tachograph when drivers switch active roles.
• Post-Drive Entries & Storage: Upon completing the journey or shift, the driver must record the end location, date, and final odometer reading on the disc before removing it. These used discs are personal records and must be properly stored by the transport operator for legal compliance and potential inspections.

Legal Requirements and Regulations in Germany

In Germany, the use and management of tachographs and diagram discs are primarily governed by the Fahrpersonalverordnung (Driving Personnel Ordinance), § 57a of the Straßenverkehrs-Zulassungs-Ordnung (StVZO – Road Traffic Licensing Regulations), and key European Union regulations, specifically EU Regulation (EEC) No. 3821/85 and EU Regulation (EC) No. 561/2006.

These regulations mandate that commercial vehicles for goods transport with a permissible gross vehicle mass (GVW) over 3.5 tonnes (including trailers) and vehicles for passenger transport with more than nine seats (including the driver), when used commercially within AETR states, must be equipped with a tachograph. The devices must be sealed and regularly calibrated. The primary goal is to monitor drivers' compliance with driving and rest times, prevent fatigue, enhance road safety, and ensure fair competition.

Driver Responsibilities: Drivers are required to correctly fill out, use, and carry their current diagram disc, along with discs from the previous 28 calendar days (this period will extend to 56 days under the EU Mobility Package). They must present these records to authorities upon request during roadside checks.

Operator Responsibilities: Transport operators have significant obligations, including:

• Ensuring drivers are properly instructed on tachograph use.
• Organizing work schedules to allow drivers to comply with regulations.
• Archiving diagram discs chronologically for at least one year (two years if also used as working time proof).
• Regularly checking records for compliance.

Violations of these regulations can lead to substantial fines for both the driver and the transport operator in Germany and other EU member states.

Diagram Discs vs. Digital Tachographs

Diagram discs are a feature of analogue tachographs, which were standard until May 1, 2006. From this date, all newly registered commercial vehicles subject to EU driving and rest time regulations were mandated to be fitted with digital tachographs. Digital systems replace paper discs with a driver smart card and an internal memory unit within the vehicle, recording data electronically.

While digital tachographs offer enhanced security against manipulation and more efficient data management, analogue tachographs using diagram discs are still valid and in use in many older vehicles. The EU Mobility Package continues to evolve these regulations, with future changes including the introduction of 'Smart Tachograph Version 2' (G2V2) and an expansion of tachograph requirements to commercial vehicles with a GVW of 2.5 tonnes or more from 2026.

Preventing Manipulation and Ensuring Accuracy

The integrity of diagram discs is paramount for ensuring accurate enforcement of driving and rest time regulations. Historically, analogue tachographs were susceptible to various forms of manipulation, such as bending recording styluses, inserting foreign objects to block recording, or failing to insert a disc at all. Manual time adjustments on older devices could also be used to obscure overruns of driving times.

Such manipulations are strictly illegal in Germany and across the EU. Authorities employ sophisticated methods, including microscopic analysis of discs after accidents, to detect falsification. The development of digital tachographs was partly driven by the need for more tamper-resistant recording systems, which use encryption and detect unauthorized interventions. Any attempt to manipulate a diagram disc carries severe legal consequences for drivers and operators, emphasizing the importance of honest and accurate record-keeping for road safety and regulatory compliance.

Exceptions to Tachograph Requirements in Germany

German and EU regulations provide specific exemptions where tachographs, and thus diagram discs, are not mandatory. These exceptions are crucial for drivers to understand, as operating under an exemption means different rules may apply regarding record-keeping.

Key exemptions in Germany include:

• Vehicles used for regular passenger transport services where the route length does not exceed 50 km.
• Vehicles with a permissible maximum speed not exceeding 40 km/h.
• Vehicles used for non-commercial transportation in humanitarian or medical aid operations.
• Vehicles owned or rented without a driver by the armed forces, police, civil protection, fire brigades, or forces responsible for maintaining public order, provided the transport is undertaken due to the tasks assigned to these services and is under their control.
• Vehicles specifically used for breakdown assistance within a 100 km radius from their base.
• Vehicles undergoing road tests for technical development, repair, or maintenance, as well as new or rebuilt vehicles not yet put into service.
• Vehicle combinations with a permissible maximum mass not exceeding 7.5 tonnes used for non-commercial goods transport.
• Specific national exemptions for agricultural and forestry vehicles, and certain craft businesses operating within a 100 km radius of their base, as detailed in § 18 FPersV.