I thought also that the exercise was quite well structured because the student could create a system to test his work and was able to conclude on his own by pressing buttons and watching LEDs that the truth table he had put together failed.
Of course, like a lot of these school exercises, there is an attempt to relate them to a real world situation so it does not appear too abstract to the student. However, a lot of the complexity of the real world situation has to be stripped out to make it a manageable problem. That is OK because, presumably, this is an exercise in logic and not in traffic management. However, such simplifications, when completely unrealistic, can cause confusion.