Public Transport Capacity Analysis Procedures for Developing Cities
Bus Berth Capacity in More Complex Service Configurations
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- Figure 3‑3 Plan View of Transmilenio Bus Station
- Table 3‑9 Service Variability Levels
- Service time variability
- Headway variability
- Figure 3 ‑4 Transmilenio Station (Bogota) With Long Queue Table 3‑10 Bus Berth Capacity (uninterrupted flow) for a Station with a Single Berth
- Mean Service Time (sec.) Case Berths
Bus Berth Capacity in More Complex Service ConfigurationsThe US transit capacity manual has procedures for determining the increase in capacity with successive berths at a bus stop. The operating system for this analysis assumes that each arriving bus accesses the first vacant berth and that buses can board and discharge customers at any berth. In cases where the stop serves multiple routes, passengers must observe the location of arriving buses in order to board the proper vehicle. In several circumstances outside of the US, the service operating system is quite different. Transmilenio in Bogota is a case in point. The Transmilenio running way consists of two lanes in each direction and buses are able to pass each other in most circumstances. Most of the stops are served by several routes. The routes are partitioned into route groups and the group is assigned to a single berth. A plan view of a typical station is shown in Figure 3 -3 below. Note that some stations have two or three such modules. 
Figure 3‑3 Plan View of Transmilenio Bus Station In the figure berth 2 has a queuing space behind it in the boarding lane. Boarding and discharging is not done in the queuing space. The queuing space can be accessed from the bypass lane. The set of routes assigned to berth 1 is distinct from the routes assigned to berth 2. In order to present a set of tools to analyze this and other situations, a set of simulation models was developed to determine the capacity of the following four configurations: Single loading berth – no queuing space Single loading berth – queuing space for one bus Dual loading berth – no queuing space Dual loading berth – queuing space for one bus Capacity was defined for several acceptable failure rates including (5%, 10% and 25%) with the failure rate being defined as the probability that an arriving bus will not be able to enter either a vacant berth or a queuing space. Other variables in each of these assessments included mean service time with values of 20, 20, 40, 50, 60 and 75 seconds4. The final two input variables were service time variability and arrival rate variability. To simplify the assessment, these two variables were staged as either high or low. Definitions are shown in the table below. Table 3‑9 Service Variability Levels
* Coefficient of variation = standard deviation/mean This analysis resulted in the development of 8 tables – two for each of the four service domains described above and the presence or absence of a traffic signal at the station. These are shown in tables 3-22 through 3-29. A summary table appears in Table 3 -10 Bus Berth Capacity (uninterrupted flow) for a Station with a Single Berth These tables require relatively little data collection effort to estimate station capacity. On high volume BRT services, mean service times can be obtained with about an hour’s worth of observations. A similar length of time would enable a determination of low or high values of service time and headway variability. These data are for articulated (18m) buses. Non-articulated (13 m) buses are likely to increase capacity slightly since the time for the bus to clear the station is about 5 seconds less. Conversely, a bi-articulated bus takes 7-8 seconds to clear the station. The determination of an acceptable failure rate is more complex. In cases where some buses bypass certain stops, the inability of buses serving the stop to access either the berth or the queuing area may result in blocking through buses. In such cases a low failure rate of about 10% is suggested. In high volume cases, a high failure rate may result in a queue which may not dissipate for a long time, perhaps as much as several minutes. The photograph (Figure 3 -4) below shows a long queue at a TM stop. Fortunately, this dissipated within 2 minutes. 
Figure 3‑4 Transmilenio Station (Bogota) With Long Queue Table 3‑10 Bus Berth Capacity (uninterrupted flow) for a Station with a Single Berth
Table entries are capacities in vehicles per hour with a failure rate of 10% with moderate service time variation and moderate headway variation. In this table, dwell time includes time to enter the stop, and time to depart the stop. This is about 15 seconds. * If yes, green to cycle time ratio is 0.5 Directory: curated curated -> Concept stage curated -> Concept stage curated -> Republic of Côte d'Ivoire Urbanization Review curated -> Report No: aus11011 Central America curated -> Report No. 94474-pk fiscal Disaster Risk Assessment Options for Consideration curated -> Environmental and Social Management Framework for the Costa Rica Telecommunications Sector Modernization Project curated -> Environment Impact Assessment For Jiangxi Shangrao Sanqingshan Airport Beijing Guohuantiandi Environmental Technology Development Center. Ltd. Oct. 2012 Content curated -> Growth through Innovation An Industrial Strategy for Shanghai By Shahid Yusuf Kaoru Nabeshima April 22nd, 2009 curated -> Report No: 70178. People's Republic of China Download 2.52 Mb. Share with your friends:
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