Part of the Union Pacific Railroad’s answer is in a Precision Measurement Vehicle (PMV). To develop and improve the company’s infrastructure, the PMV is used to provide accurate locations and detailed descriptions of all facilities that can be seen and measured from the track.
Global Positioning System (GPS) data from the PMV provides the location of control points and road crossings to the Positive Train Control system. Other sensors on the PMV mobile survey platform include a high-definition, 360-degree video that captures and acquires data using optical distance measurement wheels, an advanced inertial navigation system and under-vehicle mounted cameras. The data is transmitted to the railroad’s Positive Train Control (PTC) system.
Part of the safety aspect of managing its infrastructure, PTC also uses GPS data from moving trains to automatically stop a train and prevent accidents. In particular, PTC is designed to prevent:
- Train-to-train collisions
- Derailments caused by excessive train speed
- Train movements through misaligned track switches
- Unauthorized train entry into work zones.
Since the tracks and foundation are a critical portion of railroad safety, measuring the deflection of the track under load is another area where sensing is employed. In his PhD dissertation, Sheng Lu describes a process to measurement real-time vertical track deflection. The test vehicle, a coal hopper, used GPS, a camera and lasers as the sensors. Solar panels and a battery energy storage provided the power for the system so the image data processing and computing could be performed on the vehicle.
Measurements of the distance between the camera image plane and the rail surface, h. are used to calculate the displacement of the rail surface with respect to the wheel/rail contact plane, Yrel. The Yrel, value is related to ywheel, the absolute rail deflection of the wheel/rail contact point (with respect to the unloaded rail).
From these three examples, it is clear that sensing plays a critical role in railroad maintenance and safety.