Taipei Rapid Transit System Research Articles

Analysis of Aerosol Composition and Assessment of Tunnel Washing Performance within a Mass Rapid Transit System in Taiwan

ABSTRACTThe metro system is the main mode of transportation in Taipei City. The air quality of metro stations is crucial for passengers. This study investigated particle size distribution and its elemental composition and assessed tunnel washing performance in the Taipei Rapid Transit System (TRTS). A 24-hour particle sampling process was performed in the tunnels, platforms, and entrances and exits to measure particulate matter (PM)2.5 and PM10 concentrations in an underground metro station and to analyze PM metal components. PM10 and PM2.5 concentrations decreased sequentially from the tunnels to the platforms and then to the entrances and exits to ambient environment in the metro station. The main metal components of suspended particulates in the TRTS mainly included iron, barium, copper, manganese, magnesium, aluminum, chromium, zinc, nickel, and lead. The total PM10 and PM2.5 metal proportions were 33.9%–24.7% and 32.9%–22.8%, respectively. Furthermore, the effectiveness of tunnel washing in reducing the PM concentration was investigated. Monitoring results showed an increase in PM10 and PM2.5 concentrations after tunnel washing on the first day. The PM concentration started to decrease from the second day. Furthermore, 3.5 months after tunnel washing, the PM10 concentration decreased by 45.9%, and 2 months after tunnel washing, the PM2.5 concentration decreased by 71.3%. The mechanism of the continuous reduction in the PM10 concentration after cleaning is probably related to the porous material of tunnel walls, which may provide a deposition sink for aerosol particles, as well as the filter effect of the air conditioning system. This is the first study to use full-section tunnel washing to reduce PM exposure at mass rapid transit (MRT) stations. Although full-section tunnel washing reduced the PM concentration in the metro station, accessorial technology, such as the air conditioning system or platform design, may help in reducing the exposure of MRT passengers.

Indoor Air Quality in the Metro System in North Taiwan.

Indoor air pollution is an increasing health concern, especially in enclosed environments such as underground subway stations because of increased global usage by urban populations. This study measured the indoor air quality of underground platforms at 10 metro stations of the Taipei Rapid Transit system (TRTS) in Taiwan, including humidity, temperature, carbon monoxide (CO), carbon dioxide (CO2), formaldehyde (HCHO), total volatile organic compounds (TVOCs), ozone (O3), airborne particulate matter (PM10 and PM2.5), bacteria and fungi. Results showed that the CO2, CO and HCHO levels met the stipulated standards as regulated by Taiwan’s Indoor Air Quality Management Act (TIAQMA). However, elevated PM10 and PM2.5 levels were measured at most stations. TVOCs and bacterial concentrations at some stations measured in summer were higher than the regulated standards stipulated by Taiwan’s Environmental Protection Administration. Further studies should be conducted to reduce particulate matters, TVOCs and bacteria in the air of subway stations.

Rail-to-Earth Resistance Assessment: A Medium Capacity Transit System with Continuous Negative Rails by Potential Measurement

The Brown Line of the Taipei Rapid Transit System is the only rubber-tire medium capacity line in the system. The first phase of its construction was launched in 1988, and revenue service began in 1996. It was frequently referred to as the Muzha Line, as the route runs from the Taipei Zoo in the southeast suburb of Muzha to the vicinity of the Taipei Songshan Airport in the northeast side of the downtown commercial district [1]. The two-track line was built on single reinforced-concrete beam structures supported on reinforced-concrete columns [2], except in a short tunnel. The second phase was an extension to the Taipei Songshan Airport terminal and then to the suburb of Neihu, so it was also referred to as the Neihu Line. The section of the second-phase route near Taipei Songshan Airport was built in an underground tunnel, while the rest of the route was built on single reinforced-concrete beam structures supported on reinforced-concrete columns, like the Muzha Line. Figure 1 shows the schematic route map of the Brown Line with labeling of selected stations. Note that the stations of the first phase were labeled as BR2 through BR13, and the stations of the second phase were labeled as B1 through B11, plus BR1 as the Taipei Songshan Airport Station.

Characterising the failure pattern of a station box of Taipei Rapid Transit System (TRTS) and its rehabilitation

The case history where flooding due to the leakage through the openings in diaphragm wall accompanied by piping in excavation bottom severely affected the construction of a station box of Taipei Rapid Transit System (TRTS) is presented. The emergency grouting adjacent to but outside the diaphragm wall was conducted following the leakage. However, injection pressure due to slow setting time of grout not only aggravated the piping but also caused the side effect deflecting the diaphragm wall toward excavation area. The severe piping quickly washed the soil into station box and the differential settling of buildings above along with propagating surface cracks forced the use of water emplacing in station to ease the piping and further ground loss; meanwhile, seal grouting and void filling grouting were undertaken to facilitate the rehabilitation of foundation construction through which the station box was opened subsequently. Based on analyzed interactive behaviour between water emplacing or injection pressure and wall deflection or brace load, the diaphragm wall and bracing system would not have functioned normally during grouting if water had not been introduced in the station. The cause of opening in the diaphragm wall is triggered by the abnormal concrete placement which can be avoided through the suggested procedure of examination. The paper discusses the insights into a review of instrument records and provides the lessons learned.

Applicability of the principle of superposition in estimating ground surface settlement of twin- and quadruple-tube tunnels

Prediction of tunneling-induced ground surface settlement is important to underground constructions in the densely populated city because excessive settlement could trigger potential damage to existing structures. This paper examined the interaction of multi-tube tunnels on ground surface settlement and the methods of prediction for the transverse ground surface settlement profile induced by the closure and grouting of tail void of shield machine of multi-tube tunnels in the CH221 Contract of the Taipei Rapid Transit System. The transverse ground surface settlements of a twin- and a quadruple-tube tunnels at two sections of this contract were back analyzed using the empirical equation that assumed the settlement profile over a tunnel to be a Gaussian distribution curve, and the finite element analysis. The applicability of the principle of superposition in the analysis and the characteristics of the ground surface settlement for a green-field land (previously undeveloped land) and a brown-field site (previously developed site) was also studied using the finite element analysis. The results showed that the ground surface settlement profile of multi-tube tunnel could be conveniently and reliably estimated using the empirical equation together with the principle of superposition. Extra effort required in the model set-up and result interpretation caused the numerical method to be outperformed by the empirical method.

Shield machine disassembly in grouted soils outside the ventilation shaft: A case history in Taipei Rapid Transit System (TRTS)

During the construction of the ventilation shaft A of the Luzhou Line of Taipei Rapid Transit System (TRTS), the shield machine obliged to disassemble in grouted soils outside the shaft as the excavations in the shaft were still in progress. This paper describes the use of ground improvement followed by cement and chemical grouting as well as dewatering to both reduce the water ingress to acceptable volumes and the piezometric pressures in an alluvial silty sand layer during the shield disassembly task. In addition, the chamber sealing and bulkhead installation were designed to prevent the tunnels and shaft from any accident through which the tunnel would subsequently pass.

Analysis of Rail Potential and Stray Currents in a Direct-Current Transit System

The diode-grounded scheme for stray-current collection in some systems, such as the Taipei rapid transit systems (TRTS), has been constructed to gather the stray current leaking from the running rails and avoid corrosion damage to the system as well as the surrounding metallic objects. During operation of the TRTS, a high potential between the negative return bus and system earth bus at traction substations, referred to as rail potential, has been observed on the Blue line between BL13 and BL16. Since the Blue and Red-Green lines have their running rails and stray-current collector mats in junction at the G11 station, the TRTS suspects that the impedance bond at G11 is the cause of rail potential rise. This paper presents the results of field tests for studying whether the impedance bond at G11 of the tie line has an impact on rail potential and stray currents in TRTS. The results show the rail potential can be reduced by disconnecting the impedance bond at G11 of the tie line so that the negative return current of the Blue line cannot flow to the rails of the Red-Green Line, and vice-versa. In addition, rail potential and stray currents occurring at a station of the Blue line are numerically simulated by using a distributed two-layer ladder circuit model. The simulation results are compared with the field-test results and they are consistent with each other.

Measurement of Particle Mass Concentrations and Size Distributions in an Underground Station

The Taipei main station is a major transfer station in the Taipei Rapid Transit System and is located at the center of Taipei metropolitan areas. This study investigates particle mass concentrations and size distributions at the concourse in this underground station using an optical particle counter. On-site measurements were taken during January-February 2008. Experimental results show that PM10 and PM2.5 levels in the Taipei main station were 9.83-104.26 μg/m3 and 3.84- 59.74 μg/m^3, respectively. The lognormal mass size distribution in the Taipei main station had two modes; one near 0.27 μm and the other at about 12.5 μm. Additionally, the mean mass concentrations were governed by particles with coarse PM. Measurement results also suggest that average PM10 and PM2.5 levels in the indoor station were about 0.70 and 0.53 times those outdoors, respectively. The PM levels in the indoor station and outdoors were positively correlated, indicating that PM levels at the concourse in the Taipei main station are significantly influenced by outdoor ambient PM levels. Moreover, the low PM2.5-to-PM10 ratio at the concourse in the Taipei main station was likely the result of coarse PM being re-suspended in the station concourse due to passenger movement.

Levels of ultrafine particles in the Taipei Rapid Transit System

Ultrafine particle number concentrations are measured at five stations and inside trains on four routes in the Taipei Rapid Transit System during October–December 2007. The results indicate that there are no additional emission sources of ultrafine particle on the platforms. Ultrafine particle levels at a ground level station were, however, adversely affected by traffic outside of the station. Moreover, particles can enter the underground stations via the subway tunnels resulting in high levels during weekdays.

Assessment of grounding, bonding, and insulation on rail potential and stray currents in a direct current transit system

This article presents the effects of different grounding strategies (ungrounded, direct grounded, and diode grounded), bonding, and insulation on rail potential and stray currents in the Taipei rapid transit systems (TRTSs). The TRTS is a direct current transit railway and its running rails are used as the return conductor for traction currents. The advantage is that no dedicated return conductor is required, whereas the disadvantages are rail potential and stray-current problems. Thus, the analysis of grounding strategies is important and necessary. Moreover, the effects of cross-bonding of the running rails and stray-current collector cables (traction earth conductors) are investigated since bonding is usually used to balance traction negative return currents, to reduce resistances of the negative return circuit, as well as to decrease rail potential. Meanwhile, the effects of insulation on stray currents are also described. Simulation results for the Blue line are presented in TRTS.

Upgrade of signaling system on the rapid transit systems

In this paper, discuss the upgrade system for an old type and extend to new line system of signaling at Taipei Rapid Transit Systems (RTS). Since the track circuits of fixed block are utilized the ...

Levels of PM 10 and PM 2.5 in Taipei Rapid Transit System

The PM 10 and PM 2.5 levels have been measured inside trains on four routes and on platforms at five stations in the Taipei Rapid Transit System using TSI Model 8520 DustTrak monitors. In this study, the TSI DustTrak was calibrated with a Met One E-BAM sampler within the metro station. Experimental results suggest that the TSI DustTrak overestimated PM 10 and PM 2.5 levels by about 2.0 and 2.2 times, respectively, compared with those measured by the Met One E-BAM sampler. Measurement results show that average PM 10 levels inside trains and on station platforms were 10–97 μg m −3 and 11–137 μg m −3, respectively, and average PM 2.5 levels were 8–68 μg m −3 and 7–100 μg m −3, respectively. Moreover, experimental results demonstrate that PM levels inside trains and on platforms were lower than those measured for other subway systems worldwide. Additionally, the PM 10 and PM 2.5 levels measured by ambient air-quality monitoring stations near selected metro stations correspond to PM levels in the urban atmospheric environment in Taipei. Statistical results demonstrate that average PM 10 and PM 2.5 levels in metro stations were about 0.65–1.53 times and 0.89–1.75 times, respectively, those for urban ambient air. The PM levels inside stations and outdoors are positively correlated, indicating that PM levels in the metro system are influenced significantly by outdoor ambient PM levels.

Impacts of self-selection and transit proximity on commute mode choice: evidence from Taipei rapid transit system

Debate over how land use and self-selection affect travel behavior continues. Prior research contributes limited empirical evidence to this debate, and characterizing self-selection remains problematic. This empirical research explores the impacts of self-selection and proximity to transit at both residence and workplace. The research hypothesis is self-selection and proximity to transit increase the probability of workers commuting by rapid rail transit. To conduct this research, a station-exit passenger survey was conducted along the Taipei Rapid Transit System. Analysis methods include binomial logit modeling and sensitivity analysis. Research results support the idea that transit proximity to both work and residence increase the probability of transit commuting, but the hypothesis about the impact of self-selection is only partly supported. Policy implications suggest that, on one hand, increasing density around transit stations could realize unfulfilled self-selection; on the other hand, improved quality-of-life characteristics in neighborhoods around station areas may induce residents and companies to relocate to the neighborhood, thereby increasing residents’ and workers’ probabilities of commuting by transit.

Renovation of medium capacity transit system traction electronics at Taipei Rapid Transit Systems

In this paper we present the Taipei Rapid Transit System program to replace the original DC motor drive of the medium capacity transit system trains with modern IGBT circuitry. The medium capacity transit system fleet employed traction power circuit designed in the 1980s, which soon suffered from high failure rate long before midlife overhaul. With modern power electronics technology, we replace the cumbersome drive circuitry for current-controlled power transistors by simple and straightforward gate drive circuit for voltage-controlled IGBTs. Also a large number of discrete components found on the original board are replaced by modules and ICs, improving service reliability and life expectancy

CBD Oriented Commuters’ Mode and Residential Location Choices in an Urban Area with Surface Streets and Rail Transit Lines

This study formulates a commuters' mode and route choice model as well as a households' residential choice model on a two-dimensional space. The commuters' mode and route choice model assumes that commuters select the mode and route alternative based on the least generalized travel cost. The households' residential choice model is formulated to maximize households' residential utilities subject to time and budget constraints. A simulation method is adopted to simulate household choice behavior and solve the households' residential location choice model with two-dimensional decision variables to prevent aggregation bias. A case study for Taipei metropolitan area is illustrated to analyze the variations of residential location choices for households working in the central business district (CBD) after different lines of Taipei Rapid Transit System are completed at various stages. Results indicate that (1) there is increased attraction of households in cities of Taipei County such as Pan-Chiao, Chung-Ho, Yong-Her, and Hsin-Tien due to the completion of rail transit networks and (2) residential locations better served by rail transit lines attract more households; thereby, resulting in higher residential densities.

Dynamic Analysis and Ride Quality Evaluation of Railway Vehicles – Numerical Simulation and Field Test Verification

AbstractA rather complete dynamic model with special emphases on nonlinear conicity and creep force and in consideration of random irregularity of rail profile is proposed to simulate the response and investigate the ride quality of railway vehicles. The CP341 vehicle that will soon be used in Taipei Rapid Transit System is considered in particular as the studied role model. Some of the field test data carried out for this type of vehicle are revealed as well and used for the verification of the proposed model. Both simulation and test results show that the resonant frequency of the studied vehicle is in the range of 0.6∼1 Hz, and the one-third octave root-mean-square acceleration curves of the vehicle in all studied cases meet the ride quality criteria set for the mass rapid transit vehicle systems. It is observed that the secondary suspension of the vehicle has the low frequency filtering property and the primary suspension has high frequency characteristics. A poorer ride quality in vertical direction rather than in lateral direction is also confirmed in the study. It is concluded that the proposed model can be used to simulate the dynamic response and evaluate the ride quality of any railway vehicle.

Using e-governmental indicators to build virtual value chain

The purpose of this research is to construct the e-government indicators to build virtual value chain in Taipei Rapid Transit System. Focus group interviews were used to collect the data. Content analysis and analytical hierarchy process was used to analyse the data. According to the results, the study divides the e-government indicators into seven dimensions. The research also develops 29 indicators for Taipei Rapid Transits System. These indicators can be used to help government to build virtual value chain and provide some competitive advantageous base for servicing public citizens or customers.

Safety assessment of AC earthing systems in a DC traction-supply substation

The paper assesses safety of AC earthing systems in a DC traction-supply substation (TSS) by comparing the designed mesh and step voltages to the maximum tolerable voltages. Generally, IEEE 80 criteria are based on the maximum tolerable body current to prevent fibrillation of the human heart, and this current is then translated into tolerable touch and step voltages. As a result, safety assessment of AC earthing systems in a DC TSS is referred to a procedure by which the designed mesh and step voltages are computed and compared with the tolerable touch and step voltages. Computation results of AC earthing systems for the orange line at O19 TSS in Taipei rapid-transit systems are presented as an example.

Calculation of the Frequency-Dependent Impedance of Rail Tracks Using a Four-Parameter Equivalent Tubular Conductor Model

This paper proposes a four-parameter equivalent tubular conductor model that approximates the frequency-dependent impedance of a conductor with arbitrary cross-sectional shape. The proposed model is applicable to conductors used in power cables, electric railways, printed-circuit boards, etc., in which the conductor cross-sections are irregular. An example of calculating the frequency-dependent impedance of rail tracks of the Taipei Rapid Transit System using the proposed model and the complex depth of earth return method is presented, and the results are compared with those obtained using the finite-element method.

Stack effects on smoke propagation in subway stations

In fires of subway stations, the most immediate threat to passengers' life is not the direct exposure to fire, but the smoke inhalation because it contains hot air and toxic gases. To understand the mechanisms driving the motion of smoke is therefore an important issue of fire safety, and the stack effect is found to be an important mechanism having significant influence. In this paper, we compute the three-dimensional smoke flow fields under various fires happened in a representative subway station of Taipei Rapid Transit System. To clarify the mechanisms corresponding to the stack effect, a simplified three-dimensional configuration is also considered. Results indicate that, without mechanical smoke control, the stack effect plays a decisive role and is virtually the sole factor influencing the smoke movement. Because of the stack effect, most or sometimes all of the smoke will choose a vertical shaft (usually a stairwell) to evacuate, and the cross sectional area of the shaft and the location of fire determine which shaft is chosen. Present computational results show the evidences of the importance of the stack effect and provide both valuable information to the design of the passenger evacuation routes in fires as well as criteria to the design of smoke control systems of subway stations.