The best way to maximize dart traps is to stop or slow the zombie in some fashion (electric fences, barbed wires, water, etc.), then use a trigger plate on the ground, on a 1:1 basis, to trigger the dart trap. In my builds, each dart trap is hitting the zombie 4-5 times before they pass to the next dart trap.
If you don’t slow them, they will run too fast making the dart traps worthless.