Digital tachographs work by digitally recording all data on the driver and vehicle in both its internal memory and also separately on the driver's smart card. Information must be downloaded every 90 days from the digital tachograph; and every 28 days from the driver card. The tachograph data then needs to be analysed.

Can I drive without a digital tachograph card inserted?

In order to be driving without a digital tacho card you must: ... You can only drive without a tacho card for a maximum of 15 calendar days. The DVLA is required to issue you a new card within 5 working days, so this should not be a huge problem. If your card has expired, you effectively don't have one.

Can I leave my tacho card in overnight?

Yes, you can leave your driver card in all week (company operational procedures permitting) if you want, remembering to change the mode to 'rest' and select end location before you go home and 'other work' and select start location when you arrive.