One of the most exciting recent developments is the expanded capability to measure the performance of freight cars as they roll down the track. I call this "dynamic car measurement" because it measures the action of the car as it operates, as compared to inspection of the individual components in a static environment. Though hot bearing and dragging equipment detectors have been around for a generation, these devices detect car components that have already failed. Recently, devices that measure car performance in a predictive way have become available. Their further development and deployment has great promise for rail safety, car and track maintenance, lading loss and damage, and even regulatory reform.

Since the 1970s, track geometry cars (and, more recently split-axle gauge restraint measurement cars) have been able to measure track under load to see how it behaves during the passage of a train. Valuable information from those automated testing programs went a long way toward improving track safety. Car inspection, on the other hand, relies almost entirely on visual inspection of standing cars, and the standards applied are aimed at the structural integrity of the car and its key components (flange thickness, structural cracks, etc.). Those standards generally don't address the systemic performance of a car in motion. Dynamic car measurement does.

Among the dynamic measuring devices now available to railroads, the most common is the WILD (wheel impact load detector). There are many of these deployed, and they regularly find wheels too flat to prudently or even safely continue to operate. It's not a large percentage of the wheels inspected, but it is enough to make a difference in bearing maintenance and rail integrity.