Time series models were developed to examine the long term trends with the effect of time. This model is often affected by intervention events such as a new regulation/policy, holidays, promotions, and natural disasters. On April 1, 2004, KTX (Korea Train eXpress), the first HSR (High-Speed Rail) in Korea, was introduced to Gyeongbu Line. The introduction of the KTX service led to a change in the number of passenger for Gyeongbu Line. Previous studies have analyzed the pre and post-event changes of the intervening events by simple statistics or intervention ARIMA analysis. True lab analyzed the effect of intervention event on the number of passengers using the Gyeongbu line based on the time series outlier detection which can overcome limitations in the previous studies. Time series outlier detection can analyze the time, effect type and size of an intervention event without the assumption of the time and effect type of the intervention event. The data was collected from the Korea Transport Database (KTDB) and included to the years 2003 to 2014. As a result of the analysis, the size of the influence type in the same intervention event was different for the major city routes, and the intervention event which could not be found by previous study method was found.