In recent years, construction work to excavate areas beside or beneath tracks has often been executed and a number of systems have therefore been proposed to automatically monitor such abnormal track/roadbed displacement resulting from construction work. However, conventional high-precision monitoring systems cost too much and involve cumbersome installation work, thereby unable to use readily in small-scale construction.

The RTRI has therefore developed a new high-precision track/roadbed monitoring system using a wireless sensor network, which can be set up at a cost equal to or less than half that of conventional systems (Fig. 1). The system uses plural wireless sensor units (Fig. 2) fixed to the rails with simple jigs bearing strong magnets in order to measure the inclination of rails in the longitudinal and lateral directions and determine the distribution of track displacement.

As the system does not use wires, beams or other auxiliary jigs, it affects track maintenance work less than conventional versions. The setup monitors the rail temperature that would cause buckling using a sensor built into each unit. Simple interface software enables even field workers to easily use the system, which can also be operated remotely via Ethernet.

Figure 3 shows the results of a durability test on the system with a trainload applied one million times. Although the wireless sensor unit is installed only on rail A (Fig. 2), Fig. 3 proves that the measurement is correct with both rails A and B. The RTRI has therefore confirmed the sufficient performance as a monitoring system, in that it functions correctly even with the application of one million trainloads.