Signals and Sensors The BorderTransportationSystem has dozens of points that need to be monitored, for the safety of the travelers, the animals / birds, and the equipment used.  These sensors are for the most part 'off-the-shelf' units that are fully tested and have proven reliability.  Being off-the-shelf also lowers the cost of the individual sensors, the maintenance of each, and the training of the technical staff that will be using the system. Index of ... 1,000 foot high aircraft detectors American vs Mexican vehicle and passengers Cameras to central monitoring stations Engine and car ID Every 500 feet along the route Foreign language, international signals How will heat effect the materials Internet services Microwave Tower systems Passenger unit Sensors Radar for vehicle separation Subterranean motion detectors Wall motion and infrared sensors