Fantástico. In some sense, when the vehicle was far away, you could have expressed it mathematically as $$\textrm{Vehicle} = \left(\frac{50}{100} \times \textrm{Car}\right)+ \left(\frac{50}{100} \times \textrm{Motorbike}\right)$$. Because we have no information about the vehicle, we can express it probabilistically.
But, probability is being used here due to our lack of knowledge about the vehicle. Obviously, the person(s) riding the vehicle(s) know(s) the actual truth.