EU-OPS is often quite vague or does not regulate stuff at all. Therefore some additional local regulation is usually needed. Dual basing is one of those things. However traveling time can be part of your rest time, but then it must be assured that a core sleep time of 8 hours plus time for physiological needs is available, time for physiological needs is one hour before and one hour after the sleep period. Which makes up the usual minimum rest time of 10 hours out of base and 12 hours at base including two hours traveling time from and to base.