(02 Jun 2019, 9:57 am)big mac wroteWhat is the actual exact rule as to which routes are required to use tachographs? For example how come the x21 isn't registered as two routes when the journey time is longer than the x9/x10?
If the route is over 50kms (around 31 mile) end to end, then a tachograph needs to be used. As with X9/X10 and many other operators, splitting the route into 2 (or more in the case of some routes), brings the mileage down, so a tachograph is not required.