I was talking to one of the locals the other day about how to stop a gate crasher. We had an idea... a cattle guard made of drill pipe. One pipe in the center isn't welded, it is free to rotate. We install cotton picker spindles thru the pipe and weld them. Now you take a smaller diameter pipe about 10ft away and connect it to a gate opener actuator. We were discussing getting a double gate opener kit that comes with two actuators and using one on a gate and the other on the spike strip. This way if some yahoo was to drive thru the gate they wont get far.

Caltrops from a cattle panel. Tractor Supply sells galvanized wire cattle panels. Cut them into small crosses with bolt cutters. Bend the crosses with a hammer in a vice or bend them over by hand.