Irregularities in railway tracks influence the running behavior of trains; large irregularities can result in poor ride comfort and in some cases derailment. Thus, it is important that the relationship between track irregularities and the running behavior of trains is identified and criteria for track irregularities are adequately established. However, the questions of how track irregularities affect the vehicle responses that determine running safety and ride comfort and how the wavelength and amplitude of each track irregularity influence the vehicle responses are barely addressed in the literature. This paper reports the results of computer simulation studies that were performed to investigate the influence of the longitudinal level, alignment and cross level of track irregularities on the running behavior of the 300 km/h KTX (Korea Train Express) train. A straight track was assumed in the calculations to ensure a focus on the effect of track irregularities. Track irregularities with various wavelengths and amplitudes were modeled using the VAMPIRE program; a vehicle dynamics modeling package that is widely utilized to study railway environments. Simulations on the effects of derailment coefficients, lateral loads, bogie acceleration and body acceleration created by track irregularities were performed to evaluate how the track irregularities affect the safety and ride comfort of the KTX. The results of the simulations indicate that track alignment has a significant impact on running safety whereas longitudinal level does not have any significant impacts.

Superimposition of horizontal and vertical curves may hamper train ride comfort and running stability and inflate maintenance costs. However, designing a track plan without superimposed curves is difficult owing to fixed points that have to be either avoided because of geographical conditions or traversed so that existing structures are utilized. This article presents a method to optimize the alignment of horizontal curves to enhance train ride comfort and running stability when horizontal and vertical curves are superimposed in the case of railway construction/renovation. An algorithm was developed to determine the combined range of radius–transition curve lengths ( R− Lt) for feasible horizontal curves that pass fixed points; it was verified through a comparison with Kufver's iterative method using Inrail software. To determine the horizontal curves for optimal ride comfort when horizontal and vertical (convex) curves are superimposed under feasible R− Lt boundary conditions, a solution algorithm was developed using the object function of ride comfort ( PCT). Finally, the simplified analysis method using PCT was verified via vehicle/track interaction analysis.

A quick-hardening concrete track has been developed to convert old ballast tracks into concrete tracks on operating lines. This method has been utilized to convert urban railways since 1997. With recent increases in train traffic and speed, maintaining track irregularities within design criteria has become essential to ensuring safety. On quick-hardening tracks, track irregularities are predominantly caused by irregular settlement around construction joints. These construction joints are inevitable in quick-hardening concrete; however, they create discontinuous sections that can affect the stable running of trains and structural durability. In this study, full-scale tests were performed with quasi-static and repeated loading on both continuous and discontinuous sections in which the earth pressure acting on the trackbed, accumulated settlement, and elastic displacement were measured. The results obtained indicate that construction joints are disadvantageous in terms of load transfer, settlement, and displacement. Additional field observations conducted on the Seoul Metro Line corroborated the results of the full-scale tests. The overall findings strongly suggest that construction joints on quick-hardening concrete tracks would need to be reinforced.

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The Personal Rapid Transit(PRT) system has been highly interested in future transportation developments due to its on-demand and optimized door-to-door transport capability. However, the major impediments to the commercialization of PRT are the high cost for construction of infrastructures as opposed to the small transport capacity and difficulty in defining the role of PRT in building a balanced transportation system. In this study, the vertical transfer device for the PRT vehicle is developed to provide more flexible and better compatible urban mobility services between means of transportation, which is expected to meet particular demands in a particular environment. This apparatus was initially designed based on the basis of vertical circulating conveyors with steel chains, which is frequently used in logistics. Its advantages are capable of the non-stop loading and reduced head-way time. Most importantly, it was intensified by the additional idea to ensure the stable and reliable transfer of the PRT vehicle fully loaded with passengers. The 1/10-scale prototype was successfully tested to demonstrate a fundamental mechanism of vertical transfer and identify unexpected user requirements prior to a real manufacturing process.