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    Posted in January 2013

    The impact of scheduling on service reliability: trip-time determination and holding points in long-headway services

    This paper presents research on optimizing service reliability of longheadway
    services in urban public transport. Setting the driving time, and thus the
    departure time at stops, is an important decision when optimizing reliability in urban
    public transport. The choice of the percentile out of historical data determines the
    probability of being late or early, while the scheduled departure time determines the
    arrival pattern for travelers. A hypothetical line and a case study are used to determine
    the optimal percentile value for long-headway services without and with holding
    points. If no holding points are applied, it is shown that the 35-percentile value
    minimizes the additional travel time to 25 % of the reference situation. In the case of
    holding, two holding points combined with a 30–60-percentile value yield the best
    performance: a further reduction of the additional travel time with 60 %.

    Read the full paper: Paper Public Transport Van Oort 2012

    Regularity analysis for optimizing urban transit network design

    Transit network planners often propose network structures that either assume a certain level of regularity or are even especially focused on improving service reliability, such as networks in which parts of lines share a common route or the introduction of short-turn services. The key idea is that travelers on that route will have a more frequent transit service. The impact of such network designs on service regularity is rarely analyzed in a quantitative way. This paper presents a tool that can be used to assess the impact of network changes on the regularity on a transit route and on the level of transit demand. The tool can use actual data on the punctuality of the transit system. The application of such a tool is illustrated in two ways. A case study on introducing coordinated services shows that the use of such a tool leads to more realistic estimates than the traditional approach. Second, a set of graphs is developed which can be used for a quick scan when considering network changes. These graphs can be used to assess the effect of coordinating the schedules and of improving the punctuality.

    Read the full paper: Public Transport Van Oort 2009

    Reliability improvement in short headway transit services: Schedule-based and headway-based holding strategies

    Improving service reliability is becoming a key focus for most public transport operators. One common operational strategy is holding. Holding vehicles can improve reliability, resulting in both shorter travel times and less crowding. In this paper, both schedule-based and headway-based holding strategies are analyzed in short headway services. Despite a significant focus on holding in current literature, some important aspects have not been researched previously. The main, new, variables are the maximum holding time, the reliability buffer time and, in the case of schedule-based holding, the percentile value used to design the schedule. Both a real line in The Hague (tram line 9) and hypothetical lines are analyzed with various levels of running time variability. Both headway-based and schedule-based holding have the largest effect if
    deviations are high. When applying schedule-based holding and a maximum of 60 s. holding time is applied, the optimal value of the percentile value becomes about 65% for all lines analyzed. When no maximum holding time is applied, schedule-based holding is more effective, while there is no difference when the maximum holding time is set to 60s. This research also shows the effect of holding on crowding: An average level of irregularity of 20% could decrease to 15%, enabling either smaller capacity slack or less crowding.

    Read the full paper: Paper TRR 2010 Van Oort

    The impact of rail terminal design on transit service reliability

    Ensuring reliable rail transit services is an important task for transit agencies. This paper describes research of the effects of various terminal configurations on reliability of services. Besides terminals, the results could also be used for short turning infrastructure. Short turning is a very widespread measure to restore service after major disturbances and in many rail networks, additional switches are constructed to enable short turning.
    In this paper, it is suggested to consider reliability already during infrastructure design and the mechanisms and effects of infrastructure design are shown. Calculations of the average delay per vehicle, regarding three main types of terminals, show the effect of frequency on the one hand and occupancy time (determined by the distance from the switches to the platform (i.e. length of the terminal), technical turning time and scheduled layover time) on the other. The substantial effect of arrival variability and the number of lines using the terminal is illustrated as well. It is shown that using stochastic variables, delays will occur, although they are not to be expected in the static case. The best performance regarding reliability is achieved, when double crossovers are situated after the platforms. Single tailtracks facilitating the turning process are only acceptable if frequencies are low. Although, , they are often used in practice as short tuning facility for high frequent services. This research shows the large impact of occupancy time on expected delays. It is recommended to minimize this time by designing short distances between switches and platform and tailtracks. Capacity management is not common use in transit. However, increasing frequencies and large deviations force to consider limited capacity, while planning infrastructure. If not, delays will occur and additional measures are necessary to solve them. This could be more expensive in the long run.

    Read the full paper: Paper TRR Van Oort 2010

    Controlling operations of public transport to improve reliability: theory and practice

    RandstadRail is a new light rail system between the cities of The Hague, Rotterdam and Zoetermeer in The Netherlands. During peak hours, the frequency on some trajectories is about 24 vehicles an hour. Dealing with these high frequencies and offering travelers a high-quality product, in terms of waiting times and the probability
    of getting a seat, the operator designed a three-step controlling philosophy. The first step is to prevent deviations from occurring: the infrastructure is exclusively right of way as much as possible and at intersections RandstadRail gets priority over the other traffic. RandstadRail stops at every stop and never leaves before the
    scheduled time. The second step in the philosophy is dealing with deviations by planning additional time in the schedule at stops, trajectories and terminals. Small deviations can be solved in this way. The final step to get vehicles back on schedule is performed by the traffic control centre: they have a total overview of all vehicles
    and they can respond to disturbances like slowing down vehicles nearby a delayed vehicle. Experiencing major disturbances rerouting and shortening of lines is possible. RandstadRail has been in operation since 2007. The actual data of the performance is used to analyze the actual effects of the control philosophy. It is shown that due to the applied measures the variability of the driving times is reduced, whereas punctuality has increased. This leads to a higher level of service, creating shorter travel times and a better distribution of passengers across the vehicles.

    Read the full paper:Paper TRR 2009 Van Oort

    Line length vs. reliability: Network design dilemma in urban public transport

    Unreliability of public transport is a well-known problem. During the design stages of public transport, little attention is paid to operational reliability, although many design choices have a great impact on schedule adherence. During the network design, reliability should be taken into account as a design parameter. This paper
    deals with line length. A new design dilemma is introduced: length of line vs. reliability. Long lines offer many direct connections, thereby saving transfers. However, the variability is often negatively related to the length of a line, leading to less schedule adherence and additional waiting time for passengers. This paper suggests taking into account both the positive and negative effects of extending or connecting line . A tool is developed to calculate the additional waiting time due to variability and transfers based on actual journey and passenger data. A case study in The Hague shows that in the case of long lines with large variability, splitting the line could result in less additional travel time because of improved reliability. This benefit compensates for the additional transfer time, provided that the transfer point is well chosen. This research shows the effect of when the transfer point is chosen at stop with many and fewer passing travelers. The latter could lead to a decrease of about 30% in additional waiting time. Splitting a long line into two lines with an overlap in the central part could even result
    in more time savings. In that case, fewer travelers have to transfer.

    Read the full paper:Paper TRR 2009 Van Oort

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