Which of the following vehicles must you not overtake if you ride a motorcycle on the road, once you go past this sign?

The B-25 'No overtaking' sign shown in the picture prohibits drivers of motor vehicles from overtaking multi-track motor vehicles. As a car is a multi-track motor vehicle, you are not permitted to overtake it while riding a motorcycle. This prohibition does not apply to overtaking single-track vehicles (e.g. another motorcycle) or non-motorised vehicles (e.g. a bicycle).