I am having trouble locating solutions for a long range trigger sensor. Want to detect an approaching vehicle 300 feet or more down the road from a pole mounted device. My first thought was a laser or IR beam break sensor, but the only ones I have seen need a reflector at the target point and the unit registers the absence of the reflected beam when obstructed. I cannot put a reflector in the middle of the road.
Only device I have ever seen that works similar to what I need are laser range finders but I would have no idea how to reverse engineer one. This sensor would supplement a PIR dome lens sensor in a security application. Can't give too many specifics but the PIR works great for pedestrians. However there is an inherent delay within my system between trigger time and when the system becomes active, meaning that fast moving vehicles are long gone before the system activates.