Gate post damage by moving object through the gate

Someone keeps whacking the wooden support to my driveway gates and pathway gate around six inches off the floor - I think this is the footrest of a motor scooter which next door bring through the single gate when driveway is closed up my path to the rear of their house. THREE times it has hit with sufficient force to make my gate "drop" and split the wooden gate hinge posts. How can I best protect this point and avoid more chipped wood and damage? In other words make it immovable and not give way to anything that strikes? Would it be a big job requiring major overhall to the wooden posts which are bolted to a concrete post? Or can I apply some kind of metal protector or the suchlike? Do not worry if the offending object comes off worse - it may teach the offender to be more careful and show respect in the future. I also do not have very much money to spend on tradesmen or parts. Thank you...