The .TGD file is the specialized cryptographic container used primarily in Spain (and adopted by various European download keys) to store driver card data. While the rest of Europe predominantly uses the .DDD extension, the TGD format follows the same technical specifications defined in Annex 1B of Regulation (EC) No 1360/2002, but often includes specific wrappers for government-certified software.
Why the .TGD Extension Matters
For a transport company, the TGD file is more than just a document; it is a forensic record. Every time a driver inserts their card into a download terminal, the device extracts a binary stream of data. This stream is then digitally signed by the card's private key, creating a .TGD file that proves the driver's identity and activities without the possibility of external tampering.
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Inside the .TGD: Data Structures
A standard TGD file is composed of several Elementary Files (EF) that store specific information blocks:
EF_Card_Certificate
Contains the Public Key Infrastructure (PKI) data used by authorities to verify that the file has not been altered since it left the card.
EF_Driver_Activity
The core of the file. It logs every change in activity (Driving, Rest, Availability, Work) with a resolution of 1 minute.
Technical Differences: TGD vs. DDD
| Technical Aspect | .TGD Standard | .DDD Standard |
|---|---|---|
| Data Origin | Driver Card (Personal) | Vehicle Unit (VU) |
| File Structure | Cryptographic Wrapper | Raw Binary ASN.1 |
| Typical Size | 15 KB - 40 KB | 30 KB - 100 KB |
Common Issues when Opening TGD Files
Since TGD is a specific format, many generic tachograph viewers fail to parse the information correctly, leading to common errors:
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Signature Validation Failure: The most common error in Spanish TGD files. It occurs when the decryption tool doesn't recognize the certificate chain.
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Corrupted Data Stream: Usually caused by removing the card too early from the reader during the download process.
Legal Custody: 365 Days of Responsibility
According to EU laws, you must keep every .TGD file for at least one year. TachoTools provides a Legal Cloud Vault that automatically organizes your files by driver and date, ensuring you are always ready for a roadside inspection or a government audit.
Learn how we calculate per diems from TGD data →