This paper summarizes observations on a new development of a compact size onboard device for condition monitoring of railway tracks. Track irregularities are estimated from a vertical and a lateral accelerations and roll rate of a car body. Rail corrugation is detected by cabin noise according to spectral peak calculation. A GPS system and a map-matching algorithm are used to pinpoint the location of faults on tracks. The device is driven by a Li-ion battery for 6 hours or by outside power source. Accelerometers, rate gyroscope and GPS were designed to give higher performance. A microphone may be added outside if condition monitoring of rail corrugation is necessary. Collected data are usually kept in inside un-volatility memory (SSD) or an SD card. Data transfer module transfers the collected data to a data server via cellular phone. The compact size onboard device provides regular monitoring of tracks in order to sustain railway systems and secure the safety.