Subway PM2.5 can be substantially sourced from the operation
of the system itself. Improvements in subway air quality may be possible
by examining the potential to reduce these emissions. To this end,
PM2.5 was measured on the trains and station platforms
of the Toronto subway system. A comparison with previously published
data for this system reveals significant changes in below ground platform
PM2.5. A reduction of nearly one-third (ratio (95% CI):
0.69 (0.63, 0.75)) in PM2.5 from 2011 to 2018 appears to
have resulted from a complete modernization of the rolling stock on
one subway line. In contrast, below ground platform PM2.5 for another line increased by a factor of 1.48 (95% CI; 1.42, 1.56).
This increase may be related to an increase in emergency brake applications,
the resolution of which coincided with a large decrease in PM2.5 concentrations on that line. Finally, platform PM2.5 in two newly opened stations attained, within one year of operation,
typical concentrations of the neighboring platforms installed in 1963.
Combined, these findings suggest that the production of platform PM2.5 is localized and hence largely freshly emitted. Further,
PM2.5 changed across this subway system due to changes
in its operation and rolling stock. Thus, similar interventions applied
intentionally may prove to be equally effective in reducing PM2.5. Moreover, establishing a network of platform PM2.5 monitors is recommended to monitor ongoing improvements and identify
impacts of future system changes on subway air quality. This would
result in a better understanding of the relationship between the operations
and air quality of subways.
Increasing traffic and speeds on passenger rail lines, and a short season for maintenance work, have motivated the industry to find new methods to assess the condition of existing infrastructure and determine where upgrades are required. In this study, acceleration data from the car body and axle boxes of a revenue car over 92 km of a Canadian passenger rail route in Ontario were collected for two purposes: first, to apply weighted filtering method according to ISO 2631-1997 standard as a technique to determine the locations which highly impact the ride quality and to investigate the effect of type of track features and speed on the ride quality; second, a new analytical method called the envelope of acceleration was applied to use the recorded accelerations to evaluate the alignment and surface roughness along the track. Since the alignment and surface roughness values are always positive and are calculated over a specified length (e.g. 9.5 m, 18.9 m, 38 m) an envelope technique was employed which uses spline interpolations over local maxima of the absolute magnitude of accelerations at every separated n samples corresponding to best fit with track roughness. The regression analysis between the envelope of accelerations and alignment and surface roughness presented a meaningful correlation and showed the applied method is a promising analytical technique to indicate rough sections of the track. The limitations to the application of envelope of acceleration are also discussed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.