I need help with the following operating systems problem

In Gallap Park at Ann Arbor, there is one lane bridge. Vehicles coming from the south and the north arrive at this one-lane bridge. Vehicles heading in the same direction can cross the bridge at the same time, but vehicles heading in opposite directions cannot. And, if there are ever more than two vehicles on the bridge at one time, the bridge will collapse under their weight. If a vehicle arrives at the bridge, the number of vehicles on the bridge is less than three and they all head in the same directions, this new vehicle should be allowed to cross the bridge without waiting. Use semaphore to coordinate vehicles crossing the one-lane bridge. Write it in a pseudo code format