How to Read and Interpret Tachograph Data

A Practical Guide for Transport Managers and Restricted Operators

For any transport operator using in-scope vehicles, understanding how to read and interpret tachograph data is essential. Whether you're a Transport Manager overseeing a fleet of HGVs or a restricted licence holder with just one digital tacho vehicle, it’s your legal responsibility to ensure compliance with EU drivers’ hours rules — and that starts with knowing how to read the data.

Yet many operators and even drivers still struggle with this. Reading tachograph charts or digital data downloads isn't always intuitive, but with the right knowledge and tools, it becomes much easier to spot potential infringements, monitor working time, and stay ahead of DVSA inspections.

This in-depth guide will walk you through:

• The basics of tachograph operation

• How to read and interpret the data

• Common issues and how to spot them

• How to respond to infringements

• What records you must keep and for how long

Contents

1. What Is a Tachograph?

2. Types of Tachographs and Data Formats

3. Tachograph Symbols Explained

4. The Key Data You Need to Read

5. Interpreting Daily, Weekly, and Fortnightly Driving

6. Understanding Breaks, Rest, and Availability

7. Spotting Infringements in Tachograph Reports

8. How to Analyse Digital Data Downloads

9. Manual Entries and Their Importance

10. Smart Tachographs: What’s Different?

11. Best Practices for Data Storage and Retention

12. When the DVSA Inspects Tachograph Data

13. Training Your Team to Understand Tacho Data

14. Final Thoughts: Building a Culture of Awareness

1. What Is a Tachograph?

A tachograph is a device fitted to vehicles to record information about driving time, speed, and distance. It helps enforce EU drivers' hours rules, ensuring drivers don't exceed their legal working limits and take the required breaks and rest periods.

All HGVs (and some LGVs doing international work) used for hire or reward and weighing over 3.5t must be equipped with an analogue or digital tachograph.

2. Types of Tachographs and Data Formats

Analogue Tachographs:

• Use circular charts (discs)

• Data is inscribed via a stylus

• More prone to tampering or misreading

• Being phased out in favour of digital

Digital Tachographs:

• Use driver cards and vehicle unit memory

• Data is stored electronically and downloaded via company card

• Downloads produce .DDD files and visual reports

• Required on vehicles first registered after May 2006

Smart Tachographs (Gen 2):

• Required on new HGVs since June 2019

• Include GPS tracking, remote enforcement capability

• Record border crossings automatically

• Use DSRC (Dedicated Short-Range Communication) for DVSA roadside checks

3. Tachograph Symbols Explained

Understanding tachograph data starts with recognising the core symbols:

Symbol	Meaning
⏱️	Driving Time
⚒️	Other Work (loading, paperwork)
💤	Rest/Break
🅿️	Availability (waiting time)
⚙️	Manual Entry
🗓️	Calendar (record by date)

These symbols appear in driver cards and tacho printouts and help segment the driver’s day.

4. The Key Data You Need to Read

When reviewing tachograph data, focus on:

• Start and end of duty period

• Total driving time per day and per week

• Breaks taken – and whether correctly timed

• Rest periods – daily and weekly

• Speeding or overdriving periods

• Manual entries or gaps in data

• Infringements – flagged or noted by software

Whether you're looking at a printout, software-generated report, or .ddd file analysis, these elements form the core of compliance.

5. Interpreting Daily, Weekly, and Fortnightly Driving

Drivers under EU rules must follow strict limits:

Rule	Limit
Daily Driving Time	Max 9 hours (can be 10 twice per week)
Weekly Driving Time	Max 56 hours
Fortnightly Driving Time	Max 90 hours over 2 consecutive weeks

When interpreting the data:

• Look at cumulative totals (especially weekly/fortnightly)

• Check if 10-hour days are used more than twice

• Monitor for short breaks between long driving spells

6. Understanding Breaks, Rest, and Availability

Breaks and rest are non-negotiable for compliance.

Type	Minimum Requirement
Break	45 mins after 4.5 hours driving (can split 15 + 30)
Daily Rest	11 hours (can reduce to 9 up to 3x per week)
Weekly Rest	45 hours (can reduce to 24, if compensated)

“Availability” (e.g. waiting for loading/unloading) doesn’t count as a break unless the driver can relax freely.

Look for long stretches of driving without proper breaks – this is a red flag for DVSA inspectors.

7. Spotting Infringements in Tachograph Reports

Tachograph analysis software highlights infringements such as:

• Driving over the limit (daily, weekly, fortnightly)

• Not enough daily/weekly rest

• Break too short or missed

• Working too many consecutive days

• Failing to insert card or incorrect manual entries

Example:A driver drove 5 hours, took a 20-minute break, and drove another 4 hours — this would trigger a “break too short” infringement.

8. How to Analyse Digital Data Downloads

Every digital tacho system produces two critical data sources:

• Driver Card Data (.ddd)Includes driving, break, work, and rest activities.

• Vehicle Unit Data (.ddd)Shows vehicle usage, speed, calibration, card insert/removal.

To interpret the data:

• Use software like Tachomaster, SmartAnalysis, FleetCheck, or VDO TIS-Web

• Run weekly summaries, driver infringements reports, and working time summaries

• Export and archive reports for audits and inspections

Check that downloads are performed within legal timeframes:

• Driver card: Every 28 days

• Vehicle unit: Every 90 days

9. Manual Entries and Their Importance

Drivers must enter manual activities (e.g., work done before inserting the card or after removing it). This is crucial for:

• Accurately logging their day

• Preventing “missing data” infringements

• Supporting fair working time records

Drivers should be trained to:

• Use the tacho’s manual entry function correctly

• Input start location, activity type, and time

• Avoid falsifying rest periods

10. Smart Tachographs: What’s Different?

Smart tacho (Gen 2) features:

• Automatic GPS location logging (start, end, every 3 hours)

• Border crossing recording

• Improved anti-tamper protection

• Remote reading for enforcement officers

Interpretation basics remain the same — but you may now see GPS data in reports, giving extra context to journeys.

Coming in August 2025, all international vehicles over 3.5t must have Smart Tacho 2 installed — including retrofitting on older vehicles.

11. Best Practices for Data Storage and Retention

Record Type	Retain for
Tachograph reports	Minimum 12 months
Working time records	24 months
Infringement records and driver responses	At least 12 months
Downloaded .ddd files	12 months minimum

Store securely in digital format, ideally with automatic backups. If using paper tacho charts (analogue), store them by driver and date.

12. When the DVSA Inspects Tachograph Data

DVSA officers and enforcement agents may inspect:

• Tachograph reports during roadside checks

• Download logs showing missed or late downloads

• Evidence of manipulation or missing card entries

• Infringement rates and your response procedure

• Driver debriefing records or retraining efforts

Operators who can show clear, consistent monitoring — and that they’ve addressed any issues — fare far better than those who’ve ignored them.

13. Training Your Team to Understand Tacho Data

Driver and admin training is essential. Consider:

• Induction training for new drivers on using tacho units

• Toolbox talks on reading tacho symbols and printouts

• Admin training for downloading data and spotting errors

• Transport Manager CPD sessions on advanced data interpretation

Offer refresher training every 12 months, especially for drivers with frequent infringements.

14. Final Thoughts: Building a Culture of Awareness

Reading and interpreting tachograph data isn’t just a compliance job — it’s a safety tool. The better your team understands the data:

• The fewer infringements you’ll face

• The more efficient your operation becomes

• The stronger your position during audits or Public Inquiries

For restricted licence holders, tachograph compliance is often overlooked — but it’s one of the most common triggers for DVSA action. Understanding the data puts you ahead of the game.