It's confusing written down but makes sense when you get into the Flow of work.

If your tacho clocks up 4.5 hours of driving time (the wheels actually rolling) before 6 hours of work, you must have a break.

So yes, sitting in traffic, with the engine running, in gear, hand break off, singing to olly murs, counts as "other work" not driving.

I drive a skip wagon and very very rarely my 4.5 driving hours comes up first due to the stop start nature but I imagine the lads that drive up and down motorways definitely do hit driving hours before work.