# Indirect Assessment of Railway Infrastructure Anomalies Based on Passenger Comfort Criteria
## 6 Conclusions  
Railways are currently one of the most used mass transportation systems worldwide. The increase in the use of railway transportation demands more velocity and load capacity for trains. These two factors and weather conditions accelerate railway track infrastructure degradation, which must be assessed more frequently. The interaction between rail infrastructure, wheels, and vehicle motion creates a complex vibration environment, which is filtered by two suspension systems: primary and secondary. The former intends to induce stability and reduce the vibration transmission from track-wheels interactions, while the latter concerns the bogie-carbody transmission. These systems decrease the vibration transmission to the passenger and thus increase comfort. Railway track infrastructure, the main component of the rail industry, affects both safety and comfort; thus, it requires continuous maintenance. Currently, railway track infrastructure evaluation is mainly accomplished by inspection vehicles. However, these vehicles are expensive, and their passage disrupts programmed timetables. Based on these limitations, a low-cost CBM system was developed to identify railway track infrastructure maintenance needs based on comfort measurements without timetable disruptions. AP and IC trains ran multiple journeys along the Portuguese Northern Line, where accelerations and GPS measurements were recorded. ISO 2631 standard methodology was followed to obtain floor discomfort levels. Matching the instantaneous floor discomfort for both types of trains, railway track infrastructure maintenance sections were found. The identified geographic locations were similar to those obtained by the EM 120 inspection vehicle. Therefore, the system was validated and proven to be precise. Moreover, compared \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Zone Number**} & \multicolumn{2}{c}{**Initial Coordinates**} & \multicolumn{2}{c}{**Final Coordinates**} & \multirow{2}{*}{**Line km**} & \multirow{2}{*}{**Track Segment IP**} \\ \cline{2-2} \cline{5-6}  & **Latitude** & & & & **Longitude** & & **Latitude** \\ \hline
1 & 40.9776 & \(-\)8.6374 & 40.9753 & \(-\)8.6368 & 315 & D \\
2 & 40.9609 & \(-\)8.6354 & 40.9589 & \(-\)8.6353 & 313 & D \\
3 & 40.9005 & \(-\)8.6221 & 40.8948 & \(-\)8.6212 & 306 & D \\
4 & 40.8805 & \(-\)8.6189 & 40.8789 & \(-\)8.6187 & 304 & D \\
5 & 40.8725 & \(-\)8.6178 & 40.8708 & \(-\)8.6176 & 303 & D \\
6 & 40.7044 & \(-\)8.5727 & 40.7038 & \(-\)8.5735 & 283 & C \\
7 & 40.5196 & \(-\)8.5108 & 40.5180 & \(-\)8.5087 & 255 & C \\
8 & 40.4198 & \(-\)8.4564 & 40.4172 & \(-\)8.4566 & 242 & C \\
9 & 39.8820 & \(-\)8.6489 & 39.8807 & \(-\)8.6507 & 166 & B \\
10 & 39.0651 & \(-\)8.8734 & 39.0639 & \(-\)8.8758 & 46 & - \\
11 & 39.0081 & \(-\)8.9518 & 39.0047 & \(-\)8.9542 & 37 & - \\
12 & 38.9159 & \(-\)9.0155 & 38.9149 & \(-\)9.0160 & 26 & A \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Maintenance needs identification segments and comparison with EM 120 inspection vehicle results. with previous studies where acceleration measurements were acquired at the axle box, the application of comfort levels to assess maintenance requirements is a novelty. The developed system provides a complementary, low-cost, CBM railway track infrastructure analysis capable of detecting abnormalities (although not the type of) by using in-service passenger trains to obtain measurements, thus avoiding any service disruption. A future goal of the present research is to identify the abnormality type. Therefore, machine learning procedures will be developed and applied. Conceptualization, P.S., P.P. and J.M. ; methodology, P.S. and P.P. ; software, P.S. and P.P. ; validation, P.S., P.P., D.R., J.M. and E.S. ; formal analysis, P.S. ; investigation, P.S. ; resources, P.S. ; data curation, P.S. ; writing--original draft preparation, P.S. ; writing--review and editing, P.P., D.R., J.M. and E.S. ; visualization, P.S. ; supervision, J.M. and E.S. ; project administration, J.M. ; funding acquisition, P.S. and D.R.