We have an 850' section of one-lane driveway that curves around and up a steep hill. It is possible that you can be half way up the hill and encounter someone coming down. At that point one person has no choice but to back up, potentially for 400' on a narrow, steep road. We are looking for ideas for an alert system that will warn at the top and bottom via, say, a red light, that a vehicle sensor has been tripped at the other end of the driveway coming up/down and one needs to wait for the traffic to clear before heading up/down the hill. It would be great if this could be done with battery power but we can run 120 Volt power up the hill if necessary. I'm posting this here to get some ideas of how to hack such a system together. I hope that is how this forum works. Thanks.