Acceleration measurements inside vehicles: Passengers' comfort mapping on railways

Monitoring the status of infrastructural networks along their service life is fundamental to ensure a safe and good service quality. Due to the length and extension of infrastructures, it is fundamental to develop effective and low cost approaches that can allow a continuous monitoring. In this paper, an assessment method based on the ride comfort evaluation inside vehicles according to ISO 2631 (i.e. frequency weighted acceleration) was developed and tested on an Italian railway. In particular, the frequency weighted acceleration was calculated along the whole trip between two consecutive stops. In order to identify and localize the most critical areas along the traveling path, the vertical frequency weighted acceleration was also calculated for sub-sections of fixed lengths (i.e. 10 m) and then mapped on geographic information systems (GIS). In this way, it is also possible to determine, for example considering a railway infrastructure, whether the eventual discomfort may be due to localized irregularities or due to the passage on worn switches. Once proper threshold limit values are defined, early interventions can be planned in order to restore adequate comfort and safety levels. To test the proposed procedure, it was applied to a surface metropolitan railway characterized by an automatic guide, which granted the chance of evaluating the repeatability of the present approach. During the in-situ measurements, an inertial measurement unit (IMU) integrated together with a GPS receiver was used.