**1. Introduction**

Railway track management helps support and guide wheels and is very important in terms of comfort and safety. Track management is usually carried out by track maintenance workers and usually uses track geometry cars. However, these methods are labor-intensive and costly, and many operators cannot carry out sufficient track inspections of regional railways due to limited financial resources. To address this problem, a track diagnosis system using an exclusive onboard sensing device has been developed [1–5].

Currently, track maintenance and management on railways is based on measured data of track displacement. However, track displacement measurement requires expensive equipment such as track inspection vehicles and measuring devices. A more economical management method is required, especially for regional railways. Other methods of track management exist in addition to displacement measurement, e.g., train vibration inspection using vehicle vibration measurement, but none of them constitutes a fundamental inspection method such as track displacement inspection owing to the low reproducibility of measurement data.

Meanwhile, recent advances in the practical use of IoT devices such as smartphones incorporating accelerometers based on microelectro mechanical systems (MEMS) have been reported. These devices can be used as simple and inexpensive

vehicle vibration measurement devices. Many studies on track monitoring systems using vehicle vibration measurement with such IoT devices were conducted.

In this study, a track condition monitoring system for use on a smartphone was developed to reduce the cost of such a system. Using two types of IoT devices for business use and a commercially available smartphone, we took measurements of an actual car, compared the performance of both IoT devices, and diagnosed the condition of the track.
