Subways and Urban Air Pollution

We investigate the effect of subway system openings on urban air pollution. On average, particulate concentrations are unchanged by subway openings. For cities with higher initial pollution levels, subway openings reduce particulates by 4 percent in the area surrounding a city center. The effect decays with distance to city center and persists over the longest time horizon that we can measure with our data, about four years. For highly polluted cities, we estimate that a new subway system provides an external mortality benefit of about $1 billion per year. For less polluted cities, the effect is indistinguishable from zero. Back of the envelope cost estimates suggest that reduced mortality due to lower air pollution offsets a substantial share of the construction costs of subways. (JEL I12, L92, O13, O18, Q51, Q53, R41)

Optimized Design of Multilines Center of Subway AFC System via Distributed File System and Bayesian Network Model

Automatic fare collection system (AFCS) is a modern, automatic, networked toll collection system for rail transit ticket sales, collection, billing, charging, statistics, sorting, and management. To realize the subway transit networking operation, this paper designs the subway AFCS based on a distributed file system (DFS), namely, Gluster File System (GlusterFS). Firstly, the multiline center (MLC) in the subway AFCS is designed to analyze the status and current situation of distributed file processing in subway MLC system; secondly, the relevant technical theories are summarized, the Bayesian Network (BN) theoretical model and DFS are explored, and the principles of four DFS are comparatively analyzed; thirdly, the architecture and cluster mode of GlusterFS is expounded, and then based on GlusterFS, the architecture of subway AFCS is discussed. This paper presents several innovation points: first, the subway AFCS is designed based on GlusterFS by analyzing and aiming at the functional requirements, performance requirements, and safety requirements of the MLC subway system; second, the safety risk analysis (SRA) of AFCS is conducted from six security requirements, and a Web scanning system is designed to ensure the system data security. Finally, the design scheme is used to analyze the subway passenger flow and power consumption. The results demonstrate that the design scheme can competently adapt to three different application scenarios. Through comparison of two deployment modes of the Web scanning system, the data security Web scanning system can ensure the safe operation of the AFCS. Furthermore, the statistical analysis of subway passenger flow and power supply data shows that the proposed scheme can support the smooth operation of the subway system, which has significant practical value.

Planning Method for Urban Subway Park-and-Ride Station and Parking Berth

For satisfying the growing demand of parking in urban area and relieving traffic congestion in downtown, under the condition of urban subway park-and-ride (P&R), the methods of site selection and scale calculation of parking lots are studied. Selecting Xi'an Rd. business circle in Dalian as study object, both survey and analysis of parking demand were conducted. Based on the principle of random equilibrium selection, the logit model of P&R demand was constructed. Then the forecasting models of parking demand both in downtown and peripheral zones were proposed respectively. Using the minimum travel distance of vehicles as the objective function, site selection optimization model of P&R station was constructed. The calculation methods of scale for parking lots in both downtown and P&R station were also processed. For the case of Xi'an Rd. business circle, not only the site of P&R station was planned, but the scale of parking berth was calculated. According to the plan and calculation, the total number of parking berth has increased from 3380 to 4011. Among the planned berths, 75.7 % are in the business circle and 24.3 % in P&R stations are outside downtown. Thus, the number of planned berths in the business circle has actually decreased by about 8 %. The research indicates that, for downtown with subway system, by reducing parking berths in downtown and increasing them in P&R stations outside the urban area, this planning method is more beneficial to relieve the problems of parking and traffic congestion in downtown than traditional method.

Identifying Subway Passenger Flow under Large-Scale Events Using Symbolic Aggregate Approximation Algorithm

Various social events, such as holidays, important sporting events, and major celebrations, may result in sudden large-scale passenger flows in certain sections and stations of urban rail transit systems. The sudden inbound passenger flows caused by these events can easily lead to continuous congestion of the subway network, which has a profound impact on the safety, reliability, and stability of a subway system. Because of the large magnitude of swipe data and the high dimensionality of time series, it is difficult to identify the emergence of such large passenger flows. Additionally, the recognition accuracy of the existing identification methods cannot meet the operational monitoring requirements. To address the above-mentioned issues, this paper proposes an optimized symbolic aggregate approximation (SAX) algorithm to identify historical sudden passenger flows caused by large-scale events around subways. Specifically, pre-set cluster types and dynamic time warping (DTW) are proposed to enhance the matching rate. Compared with the K-means method, the proposed method exhibits an average increase of 30% in mining accuracy, and the calculation time is shortened to one-sixteenth of the original value.

Assessing Impacts of New Subway Stations on Urban Thefts in the Surrounding Areas

Whether newly implemented public transit stations influence the nearby crime pattern has been debated for years. In ZG City, China, 2 new subway lines and 20 new stations were implemented in 2017. This intervention allows us to test the plausible relationship between new public transit stations and thefts in the surrounding areas. We use the difference-in-differences (DID) model to assess the theft in the treatment and control areas before and after the implementation of the new stations, with necessary socioeconomic and land-use variables and time from the addition of the station being controlled. We also explicitly examine the impacts of the proximity of the stations and the Spring Festival on theft. The results suggest the following: (1) theft around the new subway stations significantly increases after the stations’ implementation, while the control area does not see much change in thefts; (2) proximity between the neighboring stations’ increases thefts; and (3) theft near the new stations significantly decreases during the month of the Spring Festival. This study contributes to the literature on the relationship between the subway system and crime, especially from a Chinese perspective. The finding of the research can bring insights to urban transit planning, allocation of the police force, and crime prevention.

Spatiotemporal distributions of population in Seoul: joint influence of ridership and accessibility of the subway system

Moving along with daily life, urban residents and commuters create characteristic spatiotemporal patterns which vary extensively with the time of day. These patterns are formed via traffic flows: accordingly, understanding the impact of transportation system is essential for urban planners to evaluate expected urban activities. To explore them, we examine specifically population distributions in Seoul City by analyzing hourly population data based on mobile phone location records in combination with a couple of indicators of the Seoul Subway system. Through clustering and principal component analyses, we first demonstrate that the spatial distribution of the population is categorized according to the time of day, i.e., night, daytime, and evening, variations across which reflect the morphology of land use. We then examine the influence of the subway system on the population, employing ridership and accessibility as indicators. Our linear regression analysis shows that both are associated with the daytime and the evening populations, which implies that only commercial activities are substantially coupled to the subway system. Further, we find that the distinctive difference of night population is encoded in the probability distributions; this is elucidated by means of a multiplicative growth model for the morphological evolution of Seoul, revealing decentralization of residential areas and centralization of commercial areas. This study sheds light on the interplay of a public transportation system and land use, which is of relevance to planners and policymakers wishing to develop neighborhoods in support of sustainable modes.