Before starting to overtake the driver must make sure :
Only , no driver of the vehicle behind him started overtaking
Only , that the driver of the vehicle moving in front of him on the same lane of traffic did not give a signal , that he was going to overtake another vehicle
Only in that , the lane , on which is going to cross , is free for a sufficient distance , at the same time the ratio of the speeds of the two vehicles allows overtaking in a sufficiently short time