Riding comfort for passengers in high speed trains is strongly influenced by pressure variations that occur, when train runs through a tunnel. DB's "classic" pressure comfort criteria for premium long-distance train service are based on parameters, which will significantly change with operation on new high speed lines, as trains run faster and may have increased cross-sections. Also, new lines have increasing gradients in mountainous areas and tunnel geometry changes (small cross-sections for single-track tunnels, long and inclined tunnels). Investigations indicated that existing comfort criteria will not be met and will also not be sufficient for these boundary conditions. As at the time of the study single-track-tunnels were not in operation, pressure comfort tests were conducted by DB Systemtechnik and Deutsche Bahn Innovation Management in a pressure chamber. In a quota arrangement 47 test-persons assessed 17 different pressure profiles with grades. The concept was based on past test campaigns in order to easily compare results. Grades were also asked to classify when activities like working, sleeping and communicating were not possible without interference. The results of the test-campaign show that perceived pressure comfort on the high-speed lines presently prepared for operation might be slightly lower, but still well acceptable. The derived and validated model for pressure comfort prediction implies a gradual assessment and allows comparisons between railway lines and made reserves in aural comfort exploitable, that a classic pass fail criterion would not be able to address. The reduced pressure comfort does back up the design of new German high-speed tunnels which will be designed twin-bored with single track, and thus, have relatively small cross sections (about 60.5 m~2). Based on the results obtained by this study an optimum specification for the pressure tightness of new DB high speed trains could be derived. In particular, this study supported the introduction of ICE4 service on new German high-speed line Nuremberg-Erfurt-Halle/Leipzig (VDE 8) which will start regularly in December 2017.
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