What is a .ddd file
A .ddd file is a data download from a digital tachograph. It is not a document meant
to be read: it is a signed binary container, designed to be archived and verified by enforcement
authorities. Here is what it looks like inside.
Where it comes from
A .ddd file has one of three origins, and its contents change accordingly:
| Source | What it contains |
|---|---|
| Driver card | One person's activity, accumulated on the card shift after shift |
| Vehicle unit | Activity recorded by the equipment fitted to the vehicle, covering every driver who took a turn |
| Company card | Operations carried out with the card: data downloads, tachograph locks and unlocks |
Workshop cards and control cards also exist, with formats of their own, which Tacho Converter does not handle.
Why it won't open in a text editor
The file is binary, not text. Opening it in Notepad or Excel yields a stream of meaningless characters and, at worst, damages it beyond repair — a single save is enough to alter the bytes.
The data is organised into blocks, each introduced by an identifier and its own
length. Every data block comes with a digital signature, which is what allows an
enforcement officer to establish whether the content is authentic or has been tampered with. That
is why a .ddd must be kept exactly as downloaded: renaming it is fine, editing it is
not.
The structure of the format is not an industry convention: it is laid down in Annex 1C of Regulation (EU) 2016/799, which specifies block by block how the data must be written. The link to the official text is on the official references page.
The three generations
The digital tachograph has changed over time, and a file may carry the data of a single generation or of several in parallel:
- First generation — the digital tachograph introduced from 2006 onwards.
- Second generation (smart tachograph) — adds satellite position recording and new data blocks.
- Second generation, version 2 — adds, among other things, border crossings and loading/unloading operations.
A second-generation card also carries the first-generation blocks, to stay compatible with older equipment. That is why the same piece of data can appear twice in a file: when it does, Tacho Converter gives precedence to the more recent version, which is the more complete one.
What a driver card holds
The main blocks, in the order the card organises them:
- Card identification — holder, number, validity, issuing authority, licence
- Daily activities — activity changes recorded day by day, minute by minute
- Vehicles used — plates, first and last use, odometer readings
- Places — start and end of shift, entered by hand by the driver
- Events and faults — anomalies detected by the equipment
- Special conditions — ferry, train, out of scope
- Border crossings — on newer cards only
- Loading and unloading — on newer cards only
Card memory is finite: once full, the oldest data is overwritten by the newest. That is why a file downloaded today covers a period ending today, but not necessarily starting where you would like it to.
What a vehicle unit holds
- Overview — plate, vehicle identification number, country, downloadable period
- Activities — the vehicle's day, not the person's
- Card insertions and withdrawals — who got in, when, in which slot
- Events and faults
- Overspeeding
- Calibrations — workshop interventions on the equipment
- Company locks — when a company locked or unlocked the tachograph
The vehicle unit also records detailed speed second by second, which is the bulkiest part of the download and is not carried into the PDF.
From file to PDF
Tacho Converter reads the file, works out on its own whether it is a card, a vehicle unit or a company card, and turns it into a readable PDF. Which sections make it into the document, and which do not, is set out in what is converted; how to read the result, in how to read the PDF.
This page describes how Tacho Converter works. For legal obligations, refer to the official texts.