In this car scenario, imagine that the car is moving towards positive y-direction.After the sudden brake, the whole traffic also gets the disturbance aLONG the positive y-direction.Hence the wave is longitudinal.

See work here

For transverse: Students moving up and down.This is because the displacement in up and down but the propagation is from back to forth.

For longitudinal: Students moving back and forth.This is because the displacement in back and forth and so is the direction of propagation.

See work here