Fundamentals for Urban Public Transport Systems Operations & Management

Fundamentals for Urban Public Transport Systems Operations & Management

1. Basic Operation Elements

1.1 Line, Network, Stop and Station

  • Transit Line

    • the infrastructure and service provided on a fixed alignment by vehicles or trains operating on a predetermined schedule.

  • Transit Network

    • a set of lines that connect with or cross each other and that are coordinated for efficient operation and provision of integrated services in an area.

  • Transit Stop

    • a location along a line at which transit vehicles stop to pick up or drop off passengers.

    • Facilities: signs, information, bench, shelter, ...

  • Transit Station

    • a special structure and facility for passenger boarding and alighting, waiting, and transfer.

    • Facilities: boarding platform, mezzanine, stairway, fare collection equipment, turnback and storage tracks, ...

  • Transfer Stop/ Stations

    • joint stops/stations for two or more lines at which passengers can transfer between lines, Jurong East Stn.

  • Terminal

    • end stops/stations on a transit line, e.g., Tuas Link Stn.

  • Bus Depots (or bus garage)

    • A bus depot (or bus garage) is where buses are stored and maintained. They are essential facilities for bus operations, and provide a central location for maintenance, refuelling and bus parking, along with offices and ancillary facilities that support bus operations.

  • Train Depots

    • A train depot is where trains are stabled and maintained. In Singapore, train depots support the Mass Rapid Transit (MRT) and Light Rail Transit (LRT) lines which form the backbone of the local rapid transit network. They are essential facilities for train operations, with every train line being served by at least one depot.

  • Directional line length

    • one-way distance between the two terminals along the line alignment

  • Total directional line length

    • sum of all directional line lengths

    • All the overlap routes of different lines will be counted

  • Network length

    • total length of all directional alignments served by one or more lines

    • The overlap routes of different lines will be counted only once

1.2 Vehicles, Transit Unit, and Fleet Size

  • Transit unit (TU)

    • a set of n vehicles traveling physically coupled together.

    • For single-vehicle operations such as buses, \(n=1\); for train operation, \(n>1\).

  • Fleet size \(N_f\) (unit: \(\text{veh}\))

    • the total number of vehicles needed for operation of a line or an entire network.

      \[N_f = N + N_r + N_m \]

      • where \(N\) is the number of vehicles required for regular service

      • where \(N_r\) is the number of vehicles needed for reserve

      • where \(N_m\) is the number of vehicles on maintenance and repair

1.3 Usage of Service: Passenger Volume

  • Passenger Volume \(P_k\) (unit: \(\text{prs/h}\))

    • the number of passengers travelling past a fixed point in one direction per unit time (prs/h).

    • Passenger can board and alight only at transit stops or stations, i.e., at discrete
      points along the line. Passenger volume on a given section \(k\) is:

      \[P = P_B - P_A = \sum_{i=1}^{k} b_i - \sum_{i=1}^{k} a_i \]

      • where \(b_i\) is the number of boarding passengers as the station \(i\)

      • \(a_i\) is the number of alighting passengers as the station \(i\)

  • Maximum Load Section (MLS) \(P_\max\) (unit: \(\text{prs/h}\))

    • the section on which the maximum passenger volume \(P_{\max}\) is found is called the maximum load section (MLS).

1.4 Operating Elements : Headway and Frequency

  • Headway \(h\) (unit: \(\text{min/TU}\), \(\text{h/TU}\))

    • the time interval between the moments two successive TUs pass a fixed point on a transit line in the same direction, which is usually expressed in minutes, e.g., 10 min.

    • Policy headway: headway which is determined by the minimum level of service considered acceptable for that line, i.e., the maximum headway.

    • Minimum headway: headway which is determined by the physical characteristics of the system (technology, method of driving and control, degree of safety required) and station operations (rate of boarding and alighting, departure control, etc.).

    • Clock headway: When headways \(h > 6 \min\), it is desirable to use only values divisible into 60 (7.5, 10, 12, 15, 20, 30 or 60 min), i.e., clock headways, because with them departure times at any stop fall on the same minutes in each hour, so that passenger can easily memorize the schedule.

  • Frequency of Service \(f\) (unit: \(\text{TU/min}\), \(\text{TU/h}\))

    • the number of TUs passing a point on a transit line in one direction during one hour (or some other time interval).

    • Frequency is inverse of the headway

\[f = \frac{60}{h} \qquad \Bigg| \frac{f}{\text{TU/h}} \Bigg| \frac{h}{\text{min}} \Bigg| \]

1.5 Capacity, Work and Utilization

  • Line Capacity \(C\) (unit: \(\text{sps/h}\))

    • the maximum number of spaces that can be transported past a fixed point in one direction during one hour. (dynamic capacity)

    • 1 \(\text{sp}\) represents 1 space for one passenger (spaces)

      \[C=C_{v} \cdot c=C_{v} \cdot n \cdot f_{\max } \qquad \Bigg| \frac{C}{\text{sps/h}} \Bigg| \frac{C_{v}}{\text{sps/veh}} \Bigg| \frac{c}{\text{veh/h}} \Bigg| \frac{n}{\text{veh/TU}} \Bigg| \frac{f}{\text{TU/h}} \Bigg| \]

    • where transit units per hour \(f_{\max}\) (unit: \(\text{TU/h}\)): the maximum frequency that can be physically achieved on a line under given conditions.

    • Vehicles per hour \(c\) (unit: \(\text{veh/h}\)): the maximum number of vehicles that can pass a fixed point on a line in one direction during one hour, \(c = n f_{\max}\).

  • Vehicle Capacity \(C_v\) (unit: \(\text{sps/h}\))

    • the maximum number of spaces for passengers a vehicle can accommodate. (static capacity)

  • Scheduled Line Capacity \(C_o\) (unit: \(\text{sps/h}\))

    • the number of spaces transported past a fixed point in one direction during one hour under a given operating schedule.

  • Utilization coefficient of scheduled line capacity \(\delta\) (non-unit)

    • ratio of scheduled to absolute capacities of a line.

    \[\delta = \frac{C_o}{C} \qquad \Bigg| \frac{\delta}{-} \Bigg| \frac{C_o}{\text{sps/h}} \Bigg| \frac{C}{\text{sps/h}} \Bigg| \]

  • Utilized capacity \(P\) (unit: \(\text{sps/h}\))

    • the maximum number of passengers per hour that are actually transported.

  • Capacity utilization coefficient / load factor \(\alpha\) (unit: \(\text{prs/sp}\))

    • ratio of utilized to offered capacity of a line

    \[\alpha = \frac{P}{C} \qquad \Bigg| \frac{\alpha}{\text{prs/sp}} \Bigg| \frac{P}{\text{prs/h}} \Bigg| \frac{C}{\text{sps/h}} \Bigg| \]

  • Offered work \(w_o\) (unit: \(\text{sp-km(/h)}\), space-km/h)

    • the quantity of offered service on a transit line, expressed in space-km/h.

    \[w_{o}=C \cdot L=f \cdot n \cdot C_{v} \cdot L \qquad \Bigg| \frac{w}{\text{sp-km(/h)}} \Bigg| \frac{C}{\text{sps/h}} \Bigg| \frac{L}{\text{km}} \Bigg| \frac{f}{\text{TU/h}} \Bigg| \frac{n}{\text{veh/TU}} \Bigg| \frac{C_{v}}{\text{sps/veh}} \Bigg| \]

    • where \(L\) is the entire length

  • Utilized work \(w_p\) (unit: \(\text{prs-km(/h)}\), passenger-km/h)

    • the passenger-km/h traveled on the line

    \[w_{p} = \sum_{i} p_{i} \cdot S_{i} \qquad \Bigg| \frac{w}{\text{prs-km(/h)}} \Bigg| \frac{p_i}{\text{prs/h}} \Bigg| \frac{S_i}{\text{km}} \Bigg| \]

    • where \(p_i\) is passenger volume on section \(i\) of the line;

    • \(S_{i}\) is the length of section \(i\) of the line

  • Work utilization coefficient \(\bar{\alpha}\) (unit: \(\text{prs-km/sp-km}\))

    • ratio of scheduled to absolute capacities of a line

    \[\bar{\alpha} = \frac{w_p}{w_o} \qquad \Bigg| \frac{\bar{\alpha}}{\text{prs-km/sp-km}} \Bigg| \frac{w_p}{\text{prs-km(/h)}} \Bigg| \frac{w_o}{\text{sp-km(/h)}} \Bigg| \]

1.6 Travel Time

1.6.1 On-line Travel Time

  • Running time \(t_{r}\) (unit: \(\text{min}\), \(\text{s}\))

    • the time interval between a TU's starting from one stop and stopping at the next one, i.e., the net travel time between stops.

  • Station standing/dwell time \(t_{s}\) (unit: \(\text{min}\))

    • the duration of a TU's standing at a stop for the purpose of boarding and alighting of passengers.

  • Station-to-station travel time \(T_{s}\) (unit: \(\text{min}\))

    • the time interval between a TU's departures from two adjacent stops.

    \[T_{si} = t_{ri} + t_{si} \qquad \Bigg| \frac{T,t}{\text{min}} \Bigg| \]

  • Operating time \(T_o\) (unit: \(\text{min}\))

    • the scheduled time interval between a departure of a TU from one terminal and its arrival at the other terminal on the line.

    \[T_o = \sum_{i} T_{si} = \sum_{i} (t_{ri} + t_{si}) \qquad \Bigg| \frac{T,t}{\text{min}} \Bigg| \]

  • Terminal time \(t_t\) (unit: \(\text{min}\))

    • the time a TU spends at a line terminal.

    • Total terminal time at both terminals: \(t_t' + t_t''\)

    • Terminal time is provided for some or all of the following purposes:

      • Vehicle turning or change of driver's cab

      • Resting of the crew

      • Adjustment in schedule (e.g., to maintain uniform headway)

      • Recovery of delays incurred in travel

  • The percent of operating time \(\gamma\) (unit: \(\%\))

    \[\gamma = \frac{t_t' + t_t''}{2T_o} \times 100\% \qquad \Bigg| \frac{\gamma}{\%} \Bigg| \frac{T,t}{\text{min}} \Bigg| \]

    • The value of \(\gamma\) usually varies between 10% and 30%

  • Cycle time \(T\) (unit: \(\text{min}\))

    • the total round trip time on a line, or the interval between the two consecutive times a TU in a regular service leaves the same terminal. It consists of operating times for the two directions and terminal times at both terminals.

    \[T = T_o' + T_o'' + t_t' + t_t'' \quad \text{or} \quad T = 2(T_o + t_t) \qquad \Bigg| \frac{T,t}{\min} \Bigg| \]

  • Deadhead time \(t_d\) (unit: \(\text{min}\))

    • the portion of TU travel time during which the TU is not in passenger (revenue) service. It includes travel from depot to the line and back, or between lines when a TU is reassigned.

  • Platform time \(T_p\) (unit: \(\text{min}\))

    • the total time a TU is in operation. When a TU makes \(k\) round trips on a line and has both deadhead times equal, its platform time:

    \[T_p = kT + 2 t_d \qquad \Bigg| \frac{T,t}{\text{min}} \Bigg| \]

1.6.2 Passenger travel times

  • Access time \(t_a\) (unit: \(\text{min}\), \(\text{s}\))

    • the time which an individual passenger requires for approach to a transit stop or departure form a stop to his destination for a give trip.

    • Land Transport Master Plan 2040: "8 in 10 households living within 10
      minutes' walk of a train station by 2030."

  • Waiting time \(t_w\) (unit: \(\text{min}\), \(\text{s}\))

    • the time between passenger arrival at a stop and the time of TU departure.

    • For frequent transit service, the average waiting time is equal to half of the headway.

    • For headways \(h>6\) or 10 min, passengers begin to use a timetable and adjust their arrivals to the scheduled TU departures, so that the average waiting time becomes shorter than for random passenger arrivals and remain approximately constant for long headway.

  • On-line travel time \(t_o\) (unit: \(\text{min}\), \(\text{s}\))

    • the duration of passengers in a TU for a given trip.

  • Transfer time \(t_f\) (unit: \(\text{min}\), \(\text{s}\))

    • the time used for transferring between different lines or modes, i.e., the interval between alighting one TU and boarding another.

    • Transfer time depends on the walking time between two line platform, on headway of the second line, and on schedule coordination between the lines.

  • Origin-destination travel time \(T_{od}\)

    • the total passenger's travel time from his point of origin to his point of destination.

    \[T_{od} = t_a + t_w + t_o + t_f \qquad \Bigg| \frac{T,t}{\text{min}} \Bigg| \]

1.7 Speeds

1.7.1 Vehicle & Alignment Speeds

  • Maximum technical speed \(V_{\text{max}}\) (unit: \(\text{km/h}\))

    • the highest speed a transit unit is physically capable of achieving on a straight horizonal way under normal weather conditions when its maximum power is applied and acceleration has gradually ceased.

  • Line design speed \(V_d\) (unit: \(\text{km/h}\))

    • the maximum speed transit vehicles can achieve on a given section of line with adequate comfort and safety when physical conditions govern.

  • Legal speed \(V_l\) (unit: \(\text{km/h}\))

    • the maximum speed transit vehicles can legally operate on a given section of line. Legal speed can be changed with traffic conditions, between day and night, etc.

  • Programmed speed \(V_g\) (unit: \(\text{km/h}\))

    • the speed transit vehicles can operate meeting given standards of safety, comfort, economy, and vehicle performance.

  • Vehicle speed and alignment speeds

    • Maximum technical speed \(V_{\text{max}}\) is Vehicle speed

    • Line design speed \(V_d\), legal speed \(V_l\), programmed speed \(V_g\) are alignment speeds

    • Speeds \(V_{\text{max}}\), \(V_d\), \(V_l\), and \(V_g\) refer to physical conditions of TUs running along the line, not considering requirements to stop and related time delays.

    • \(V_{\max}\) is affected by gradient \(i\), but not by \(V_d\) and \(V_l\).

    • \(V_g \leq V_l \leq V_d\)

    • Alignment gradient, as well as different street conditions on a directionally split lines, may result in different \(V_g\)'s for the two directions.

1.7.2 Vehicle-on-line Speeds

  • Running Speed \(V_r\) (unit: \(\text{km/h}\))

    • the average speed TUs achieve from leaving one stop to arriving at the next one, denoted by \(V_r\). Running speed is usually analyzed for individual spacings. On a spacing between stops \(S_i\)

    \[V_{ri} = \frac{60S_i}{t_{ri}} \qquad \Bigg| \frac{V}{\text{km/h}} \Bigg| \frac{S}{\text{km}} \Bigg| \frac{t}{\text{min}} \Bigg| \]

  • Station-to-Station Speed \(V_s\) (unit: \(\text{km/h}\))

    • the average speed of travel between moments a TU leaves two adjacent stops, denoted by \(V_s\).

    \[V_{s i}=\frac{60 S_{i}}{t_{r i}+t_{s i}}=\frac{60 S_{i}}{T_{s i}} \qquad \Bigg|\frac{V}{\text{km/h}} \Bigg| \frac{S}{\text{km}} \Bigg| \frac{t,T}{\min } \Bigg| \]

  • Operating or Travel Speed \(V_o\) (unit: \(\text{km/h}\))

    • the average speed of TU travel along transit line with \(j\) spacings, denoted by \(V_o\). It is the speed of travel offered to the public and is therefore one of the basic elements of offered transit service performance.

    \[V_{o} = \frac{60 \sum_{i=1}^{j} S_{i}}{\sum_{i=1}^{j} T_{s i}} = \frac{60 L}{T_{o}} = \frac{120 L}{T_{o}^{\prime}+T_{o}^{\prime \prime}} \qquad \Bigg|\frac{V}{\text{km/h}} \Bigg| \frac{S, L}{\text{km}} \Bigg| \frac{t, T}{\min } \Bigg| \]

  • Cycle Speed \(V_c\) (unit: \(\text{km/h}\))

    • the average speed of a TU for a complete round trip on a line, denoted by \(V_c\). This speed is the most important one for the operator, since it directly influences the number of TUs required for a given level of services, and thus the transit line's capital and operating costs.

    \[V_{c} = \frac{60 \cdot 2 L}{T} = \frac{120 L}{T} \qquad \Bigg| \frac{V}{\text{km/h}} \Bigg| \frac{L}{\text{km}} \Bigg|\frac{T}{\min } \Bigg| \]

    • \(V_{ri} > V_{si}\) for every spacing \(i\), but both vary among spacings.

    • \(V_o > V_c\) is true for all cases, except for lines without terminal times (such as circle lines) on which \(V_o = V_c\).

  • Platform Speed \(V_p\) (unit: \(\text{km/h}\))

    • the average speed of TUs operating on a line from the time they leave depot (garage or yard) until they return to it, i.e., during the platform time, denoted by \(V_p\).

      \[V_{p} = \frac{120\left(k \cdot L+L_{d}\right)}{k \cdot T+2 t_{d}} = \frac{60 L_{p}}{T_{p}} \qquad \Bigg| \frac{L}{\text{km}} \Bigg| \frac{T,t}{\min} \Bigg| \]

      • where \(k\) is the number of round trips performed

      • \(L_d\) is the deadhead distance

      • \(L_p\) is the total distance the TU travels while absent from the depot.

    • Platform speed thus includes two deadhead trips \(L_d\) (between the depot and the line) and a number of round trips \(k \cdot L\) on the line, so that it is influenced by the location of depot in relation to the line and various schedule requirements. It is therefore used for measuring efficiency of vehicle deployment on individual lines.

1.7.3 Passengers Speeds

  • Access speed \(V_a\) (unit: \(\text{km/h}\))

    • the average speed of passenger travel to and from transit stops or stations

    • 4-5 km/h for walking; 30-50 km/h for automobile

    • This speed is important for planning and analyses of transit network layout and spacing of stops/stations.

  • Travel speed on line \(V_o\) (unit: \(\text{km/h}\))

    • the operating speed on the line section that a passenger utilizes.

  • Origin-destination Speed \(V_{od}\) (unit: \(\text{km/h}\))

    • the average speed of passenger travel along his/her path from origin to destination, including access, waiting, on-line travel and transfers, if any. For a total distance past between origin and destination \(S_{od}\)

    \[V_{od} = \frac{60S_{od}}{T_{od}} \qquad \Bigg| \frac{V}{\text{km/h}} \Bigg| \frac{S}{\text{km}} \Bigg| \frac{T}{\text{min}} \Bigg| \]

    • This speed is an element of mobility (or ease of travel) by transit, and it influences modal split.

2 Transit Travel Characteristics

2.1 Factors Influencing Transit Travel Demand

The volume of transit passengers on a line or in a network depends on the total volume of passenger travel in a city (or in a specific area) and on the level of service (LOS)/price package that transit offers as compared to the corresponding packages of competing modes, such as the private automobile, taxi, or bicycle.

Possible Factors:

  • Concentration of potential travel demand, e.g., CBD versus suburban areas

  • Transportation policy, e.g., unlimited versus controlled parking policies

  • Trip purpose, e.g., work trips versus shopping trips

  • Trip length, e.g., long trips versus short trips

2.2 Spatial Distribution of Transit Travel Demand

Distribution of travel demand by area and direction is a function of city form and land use in it.

  • The CBD and regional subcenters (or major activity centers) are generators of large travel volumes.

The transit share of travel volumes depends greatly on the type of planning and design of these centers and their relationships to transportation networks.

  • For example, if transit services are carefully incorporated with the center's design, the transit share of travel is quite significant.

2.3 Temporal Variations of Transit Travel Demand

Most of the temporal variations in transit travel are caused by the differences in travel patterns and levels of service by competing modes of transportation during different time periods.

Transit travel varies with seasons.

  • These variations, however, are not typical for all Typical Monthly Variations transit systems.

  • Variations are less pronounced in areas with diversified activities in large cities.

  • Transit service in vacation resorts or other cities dominated by a single activity usually has
    pronounced and quite different variations.

Transit travel varies with days.

  • Daily variations are relatively minor among workdays (Monday and Friday being usually the highest).

  • Daily variations are very pronounced for Saturday and Sunday. Holidays are usually similar to Sundays.

  • The difference in passenger volumes between weekdays and weekend days increase greatly when weekend trips are shifted heavily to private automobiles.

Transit travel varies with hours.

  • Hourly variations of demand are usually very pronounced on workdays, mostly because of the peaking character of commuter travel.

  • The peaking characteristics of passenger volume can be measured by the ratio of the highest hourly volume to the average off-peak hourly volume, i.e., peak-to-base ratio. This peak-to-base ratio usually varies among modes.

  • Hourly variations are less pronounced in cities with heavy, multipurpose use of transit.

2.4 Passenger Volume Analysis and Service Capacity Determination

A TU traveling on a line is plotted on the diagram as a sloped line representing its distance-time path on the diagram.

Since station-to-station speeds vary with distance between stations, the TU travel line has different slopes among spacings.

Capacity of the TU is plotted vertically. It is constant along the line, while passenger load on it varies as a function of boardings / alightings, and it reaches a maximum value \(P_{\max}\) on the MLS.

Service on the line can be imagined as a series of slices through the topography of passenger volume. Each slice represents a TU with its passenger load shown as the shaded area.

If constant service were provided throughout the day, it might not be sufficient during peak hours, particularly on the MLS, while its utilities during off-peak hours would be very low.

To satisfy the variable demand and achieve good utilization of offered capacity, service must be tailored to cover the demand as closely as possible.

This can be done in different ways:

  • Changing headway – shortening them (higher frequency) during the peaks

  • Using different TU sizes/capacities, such as different train consists (number of cars)

  • Operating TUs on certain sections of the line only ("short-turn trains"), so that the protruding topography peaks are covered by small additional TU capacity boxes

Three Methods of Adjustments of Service Capacity of Passenger Volume:

  • Variation in Headways

  • TU Consists,

  • and Length of Run

2.5 Characteristics of Travel on a Transit Line

  • Average passenger trip length \(l_{av}\) (unit: \(\text{km}\))

    • is obtained when the total passenger-km are divided by the number of passengers.

    \[l_{a v}=\frac{\sum \limits_{i=1}^{n} p_{i} \cdot l_{i}}{\sum \limits_{i=1}^{n} b_{i}}=\frac{1}{P} \sum _{i=1}^{n} p_{i} \cdot l_{i} \qquad \Bigg| \frac{l_{av}, l_i}{\text{km}} \Bigg| \frac{p_i, P, b}{\text{prs/h}} \Bigg| \]

    • where \(l_i\) intersection distance or spacing

    • \(p_i\) is the number of passengers at section \(i\)

    • \(b_i\) is the number of boarding passengers at station \(i\) (or section \(i\))

    • \(P\) is the total number of passengers boarding along the line

  • Average passenger volume \(P_{av}\) (unit: \(\text{prs/h}\))

    • is computed as the total passenger-km on the line divided by its length.

    \[P_{a v}=\frac{\sum \limits_{i=1}^{n} p_{i} \cdot l_{i}}{L} \qquad \Bigg| \frac{P_{av},p_i}{\text{prs/h}} \Bigg| \frac{l, L}{\text{km}} \Bigg| \]

  • Coefficient of flow variations \(\eta_f\) (no-unit)

    • is the ratio of the maximum volume (on MLS) and the average volume.

    \[\eta_{f} = \frac{P_{\max }}{P_{a v}} = \frac{L \cdot P_{\max }}{\sum \limits_{i=1}^{n} p_{i} \cdot l_{i}} \qquad \Bigg| \frac{l_i, L}{\text{km}} \Bigg| \frac{p_i, P}{\text{prs/h}} \Bigg| \]

    • The lowest possible value of \(\eta_{f}\) is 1, and it is found on lines with constant passenger load along their entire length (such as on CBD-Airport expresses).

    • The greater the value of \(\eta_{f}\) is, the lower the average load factor, and the more desirable are adjustments of offered service to passenger volume.

  • Coefficient of passenger exchange \(\eta_x\) (no-unit)

    • is the ratio of total passengers who board along a line to those who did not replace the alighting passengers (turnover rate).

    \[\eta_{x}=\frac{P}{P-\sum \limits_{i=1}^{n}\left|b_{i}-a_{i}\right|} \qquad \Bigg| \frac{P, b, a}{\text{prs/h}} \Bigg| \]

    • where \(b_i\) is the number of boarding passengers at station \(i\)

    • \(a_i\) is the number of alighting passengers at station \(i\)

    • The sum in the denominator consists of absolute values of differences between boarding and alighting volumes at all stations at which both occur.

2.6 Indicators of Transit Usage

Two indicators are most commonly used to express the absolute and relative magnitude of transit travel in a city; they reflect the role a transit system plays in the area and its relationship with other modes.

  • Riding habit: the ratio of annual transit rides to population of the served area, indicating how much the population utilizes the transit system. Riding habit is generally greater for large cities than for small cities.

  • Mode share: the ratio of transit travel to total travel, showing the relative role that transit plays in a city.

    • A study conducted by LTA in 2014: Hong Kong 90%, Seoul 70%, Tokyo 50%, London 30%, New York 30%

3. Characteristics, Operations and Planning of Massive Rapid Transit Systems

3.1 MRT systems

Four Definitions for MRT Systems (White, 1995):

U-Bahn: an underground railway usually running in tunnels below a city. Often termed a metro the system has reasonably close station spacing with high volumes of walk on patronage.

  • Examples:
    Singapore MRT: East-West line, North-South line, North-East line, Circle line, Downtown line
    Shanghai Metro: Lines 1-13
    Beijing Subway: Lines 1, 2, 4-10, 14-16

S-Bahn: main line surface railways with wider station spacing (2-3 kms). Peak service levels are often limited by track capacity. Sometimes S-Bahns are combined with U-Bahns through linking tunnels under cities.

  • Examples:
    Shanghai Metro: Lines 16 & 17
    Beijing Subway: Lines 13, Batong, Daxing, Yizhuang, Fangshan

Light Rail Transit (LRT): Electrically powered systems with surface operations. Systems are often developed from upgraded streetcar systems.

  • Examples: Singapore LRT: Bukit Panjang LRT, Sengkang LRT, Punggol LRT

Automated systems: train control is automatic.

  • Examples:
    Singapore MRT: East-West line, North-South line, North-East line, Circle line, Downtown line, etc.
    Shanghai Metro: Lines 1-13, 16, 17, etc.
    Beijing Subway: Lines 1, 2, 4-10, 13-16, etc.

3.2 MRT Rolling Stock

Railway rolling stock (全部机车) (i.e. railway vehicle) generally runs on hard wheels on hard rails. Wheels are both supported by rails and guided by them. Railway rolling stock includes:

  • Locomotives
  • Passenger coaches
  • Multiple units (including motive power)
  • Metro cars (usually multiple units)
  • Light rail/trams (including single and articulated units)
  • Rail mounted machines (including cranes)
  • Inspection and maintenance trolleys

Types of Light Rail Vehicle

Light Rail/Tram Type Width Floor Height
Heavy Light Rail 2.65m-2.70m Up to 350mm = low floor vehicle
Light Light Rail 2.30m-2.40m Floor height of 400-600mm = medium floor vehicle
Tramway 2.20m-2.30m Floor height 650-1000mm = high floor vehicle

The main developments in rail body design have been:

  • Lower mass
  • Higher stiffness (高硬度)
  • Higher strength

which has led to:

  • Lower energy consumption
  • Greater crashworthiness
  • Higher passenger comfort
  • Higher passenger / carbody mass ratio

3.3 MRT Track/Guideway

The main function of track is to carry the load imposed by the train and also to provide a guideway for train wheels.

The main components of track are:

  • Rail
  • Rail fastenings (which connect track to sleeper plates and sleepers)
  • Sleepers (轨枕, 枕木) (generally wood)
  • Sleeper plate
  • Ballast (压舱物, 路碴)
  • Formation: ground formation below ballast to provide support for the track

3.4 MRT Signalling Systems

Modern MRT signalling systems have the six main objectives:

  • To control trains in a safe manner for the conditions ahead
  • To maintain safe distance to any train ahead or dead-end ahead
  • To prevent the setting of conflict movements
  • To ensure that points are locked into the correct position
  • To enable trains to operate to the headway required
  • To enable trains to operate to the scheduled speed with minimal disruption consistent with safety

Two typical signaling systems

  • Fixed-Block Systems
  • Moving-Block Systems

Automatic Train Operation (ATO)
Automatic Train Supervision (ATS)

(1) Fixed-Block Systems

Detected by the wheels and axles of a train shorting a low-voltage current inserted into the rails.

Rails electrically divided into blocks

  • Short in stations
  • Longer between stations Characteristics,

Block is simply occupied or not

  • Two blocks can be occupied simultaneously
  • Two-aspect (red/green) block system
  • Two empty blocks must separate trains

Braking distance plus safety distance

Maximum 24 trains per hour typical

Up to 30 trains with shorter block lengths

  • Requires substantial training to operate

(2) Moving-Block Systems

Similar to fixed-block system with very small blocks

Continuously calculates safe distance ahead of each train and relays appropriate speed, braking, or acceleration rate

  • Requires continuous two-way communication

  • Computers that control moving-block signaling system can be on train, at a central control office, dispersed along the wayside, or a combination of these.

3.5 MRT Stations

A series of functional types for railway stations:

  • City centre terminals
  • Rail to rail interchanges
  • Bus to rail interchanges
  • Airport stations
  • Road-rail Stations
  • Rail to sea interchanges
  • Park and ride (parkway) stations
  • Suburban stations
  • Light rail stations
  • Small town and rural stations
  • Underground stations
  • Station for sports stadia
  • International passenger terminals
  • Stations within commercial developments

A number of objectives for station location planning:

  • Service major centres, activity points and transfers
  • Achieve minimum passenger time
  • Attract the maximum number of passengers
  • Achieve minimum system cost
  • Meet other requirements, e.g. inter-modal transfers, economic development, population needs, etc.

3.6 Short-term MRT Service Planning & Design

(1) MRT Capacity

Line capacity is the maximum number of trains that can be operated over a track section over typically an hour.

  • Signalling systems designed for minimum planned headway (rather than maximum capacity)
  • Speed restrictions due to sharp curves or steep downgrades on the approach to the station with the longest dwell time
  • Line crossings and merges, particularly at grade track junctions
  • Time required to turn back at a station or terminal (i.e. where a turn around is needed)
  • Mode specific issues e.g. light rail operating in mixed traffic or commuter trains sharing tracks with freight trains

The time between a train pulling out of a station and the next train entering is often the main constraining factor in rail capacity. This is often termed "close-in" time.

  • Dwell time includes Passenger flow time, Time before doors are closed, and Time after doors are closed to depart time.

  • The operating margin is the amount of time a train can run behind schedule without interfering with following trains.

  • Safe separation time is the time between consecutive trains on the same track which ensures that they do cannot collide if the front train needs to brake suddenly.

Line capacity is the maximum number of trains that can be operated over a track section over typically an hour. It is determined by:

  • Signalling systems
  • Station "close-in" Time
    • Dwell time
    • Operating margin
    • Safe separation time

(2) Line capacity constraints

Line capacity concerns the capacity to run trains due to track configuration constraints. This is one of the many factors that can limit overall capacity.

Planners must seek the "weakest link" to identify those factors which are limiting capacity overall.

(3) Passenger loading level

Typical short range planning of MRT systems entails monitoring peak loadings to ensure overcrowding standards are not breached.

Passenger Space – North American Heavy Rail Peak 15 Minutes

System \(M^2\) per Person
(Based on Gross Floor Space)
NYCT (New York City Transit) 0.38 (into CBD)
CTA (Chicago) 0.67 (into CBD)
SEPTA (Philadelphia) 0.77 (into CBD)
MBTA (Boston) 0.50 (into CBD)
BART (San Francisco) 0.53-0.83
WMATA (Washington) 0.50-1.11
MARTA (Altanta) 0.63-0.71
TTC (Toronto) 0.42-0.56
STM (Montreal) 0.31-0.38

References

[1] Vuchic, V. R., "1.1 Basic Operation Elements ", in Urban transit: Operations, planning and economics, J. Wiley & Sons, 2005, p.p. 4-22.

[2] Vuchic, V. R., Urban Transit Systems and Technology. John Wiley & Sons. Inc, 2007.

[3] The Railway Technical Website, Signalling, website

posted @ 2022-02-13 22:25  veager  阅读(184)  评论(0)    收藏  举报