Vehicle Spacing How do you keep computer controlled vehicles and railcars from crashing into each other, especially when doing up to 250 MPH?  There are several types of sensors, some that look down on a highway, some buried in a highway, some on the side of a highway, and some installed in the vehicles on the highway. Any vehicle spacing detector should be a built-in detector that can slow or even stop the vehicle if it sees a problem in the traffic lane ahead of it. The BorderTransportationSystem will have a variety of vehicles using it, and thus each will have some variations in speed, occasional breakdowns, etc., and the system due to its very high speeds will need redundancy and monitoring, as well as 'fail-safes'. Index of ... Mobileye Dual Roadside Seismic Sensor for Moving Road Vehicle Detection and Characterization Lidar Sensors Rivals Chasing Velodyne in Lidar Race SAIPS Algorithmic Solutions Velodyne Inc.