The Road Transport Directive is a subset of the Working Time Directive specifically applying to mobile workers involved in transporting goods and who are affected by the Driver's Hours regulations.
The regulations restrict any worker to an average working week of 48 hours either over set or rolling periods. The maximum anyone is able to work in a single week is 60 hours.
And don't forget, any lapse in complying OR monitoring of RTD can put you at risk of corporate manslaughter charges. More information about the Road Transport Directive (make take a while to load).