Rubber Speed Bump 6 Feet Rubber Driveway Modular Heavy Duty Speed 72.4 x 12 x 2.4 Inch Cable Protector Ramp for Garage Gravel Roads Asphalt Concrete, 6Ft-Speed Bump (2 pack 6ft speed hump)

They make rubber speed bumps that you may be able to install in your drive that will keep people from entering it. Most people hate driving over a speed bump and they have some that are less than 4 in wide that might deter most people from wanting to drive over it and then having to back across it if they use your driveway all the way. You may be able to put it near the bottom so that they only use a small portion of the driveway instead of the whole thing. The only downside is that you guys will have to drive over it but it may keep your car from being hit.Speed Bumps