The goods were not ready when the vehicle came
This is the cause that is least often written down and most often responsible. A vehicle arrives to a consignment that is still being picked, still being wrapped, or still waiting for paperwork, and every minute of that is lost from a driving day that is limited by law rather than by willingness.
It is also the cause a shipper controls entirely. A collection booked for when the goods will genuinely be ready, rather than for when the order was placed, removes it.
Driving hours, which are a legal limit and not a target
European rules cap how long a driver may drive in a day and require rest periods that cannot be shortened commercially. Beyond a certain distance a single-driver movement takes more than one working day, and no amount of urgency changes that.
The practical consequence is that an hour lost at the loading bay is not recovered on the motorway — it moves the rest period, and sometimes it moves the delivery to the following day. On a long corridor the schedule is built around the rest, not around the average speed.
Movement restrictions on the days the plan needs
Several European countries restrict heavy goods vehicle movement at weekends and around public holidays, and the rules differ by country and by cargo. A vehicle can reach a frontier precisely when it is not permitted to continue.
This is why the useful question about a delivery date is which days the vehicle would be travelling on, not only which day it arrives. The applicable position changes and should be confirmed for the specific dates rather than assumed.
The delivery point
A booked slot missed by an hour can mean a vehicle is not unloaded that day. A site without a dock or a forklift, when the vehicle has no tail lift, means it cannot be unloaded at all. Both are discovered at the address, where nothing can be done about either.
Both are also established in ten seconds at the enquiry stage, which is the whole argument for describing the delivery point rather than naming it.
The route, which is the smallest of these
Traffic, roadworks and weather do cause delay, and on most corridors they cost hours rather than days. The exception is a constrained crossing: an Alpine tunnel or pass with no near alternative turns a disruption into a stopped movement, which is why the corridor pages on this site name that risk specifically.
For the same reason, the honest thing a forwarder can say about timing is what the movement depends on, not how many hours it will take. Distance, driver hours, loading, the delivery window, restrictions and the crossing all vary per shipment, and a published number would be wrong for most of them.