Quantifying benefits of enhanced service reliability in public transport
Dr. ir. N. van Oort
Goudappel Coffeng mobility consultants / Delft University of Technology P.O.Box 16770
2500 BT The Hague, The Netherlands
E-mail: NvOort@Goudappel.nl Telephone: +31-6-15908644
Fax: +31-70-3896632
Ir. R. van Leusden BRU (Transit Authority Utrecht) E-mail: rvanleusden@regioutrecht.nl
Word count: 993
Keywords: cost benefit analysis, service reliability, tram line planning
Extended abstract prepared for the 12th international
CONFERENCE ON ADVANCED SYSTEMS FOR PUBLIC TRANSPORT
Service reliability effects on passengers
Service reliability is an important quality characteristic in public transport. However, in cost-benefit analyses, this quality aspect is rarely taken into account explicitly, since the interaction between vehicle variability and passenger reliability is complex. In our research [Van Oort 2011], we presented the main impacts on vehicle variability on passengers, being additional waiting time, a distribution of passenger travel time (and thus insecure arrival times) and crowding. In this paper we describe how to calculate these effects quantitavely and how to take them into account in a cost benefit analysis.
Figure 1 illustrates the differences and relations between the demand and supply sides. Passenger waiting time is determined by actual headways and departure times next to passenger arrival time at the stop. In addition, passenger in-vehicle time is equal to the trip time of the vehicle and together with the departure time, the arrival time at the destination stop is set. In this paper, we provide equations to translate vehicle characteristics into passenger effects. This relationship depends on the arrival pattern of passengers at their arrival stop. In a survey we found out that passenger tend to arrive at random if headways are 10 minutes or less. In that case the additional waiting time of passengers is determined by the headway variation.
Figure 1: (Interaction of) Components on demand and supply sides
Case study: tram line “Uithoflijn”
In addition to the setting up a theoretical framework, we also performed a case study. The Dutch government required a cost benefit analysis to financially support the construction of a tram line in Utrecht, the Netherlands, between the central station and the Uithof, where the hospital and university are located. Nowadays, about 30.000 passengers travel here by double articulated buses. Demand forecasts [Goudappel Coffeng 2011] show a growth towards 45.000 passengers per day in 2020. To facilitate reliable service, plans are made to shift from bus to tram services. Figure 2 shows this line, which is about 8 km long and operates about 23 x per hour per direction during the morning peak.
Departure time
Trip time
Arrival time
Headway
Supply side (Vehicle)
Waiting time
Demand side (Passenger) Arrival time at stop
In-vehicle
Figure 2: Proposed route of tram line Central station-Uithof and vv.
The main benefit transferring the bus line into a tram line is, next to less direct emissions, that service can be provided by less vehicles than in the case of bus operations. And since less vehicles are needed, the hindrance for crossing traffic (i.e. car and bike traffic) is less and more important, the probability of bunching of vehicles is limited. However, the construction and operation costs of tramways may be higher than bus operations, especially since Utrecht does not have an extensive rail network that is already available.
In the cost benefit analysis of this case we calculated the reliability benefits of transferring the existing bus system into a tram system. We compared 2 future situations (in 2020):
1 Reference case: No infrastructure will be constructed and operations will be similar to the operations nowadays (i.e. partly right of way). Capacity of infrastructure is limited.
2 Tram case: In this case the service is operated by trams with own right of way operations.
We calculated the passenger effects concerning the reduction of waiting time, distribution of travel time and the increase in the probability of finding a seat. For these calculations we used AVL data of the existing bus services. We calculated the future demand of this connection by using a demand model and simulated the new APC and AVL data, adjusting the dwell times and the level of bunching. The predicted AVL and APC data enabled us to calculate the passenger effects. In the reference case, the level of service will be very low due to high passenger demand and insufficient bus infrastructure. In case of the tram line, sufficient infrastructure is provided and besides, tram services require fewer vehicles thereby reducing the probability of bunching. We calculated the additional travel time per passenger, the distribution of travel time and the probability of having a seat as shown in table 1. Due to the high level of reliability in the tram case, the passenger effects are neglectable.
Table 1: Passenger effects of unreliability of services in reference and tram case
Reference case Tram case
Average additional travel time per passenger due to unreliable services
4,9 min 0 min
Distribution of travel times (st. dev) 2,4 min 0 min
Probability of having a seat 32% 58%
After the calculation of these values, the monetary values of these effects were calculated, using values of time, values of reliability and values of the probability of having a seat [Rand 2005]. Table 2 shows the total costs and benefits of the project [Ecorys 2011], showing the substantial contribution of improved reliability to the positive score of the cost benefit analysis.
Central Station
University
Hospital City of
Table 2: Additional costs and benefits of tram line compared to reference case
Value compared to reference case (millions in 2011)
Investment costs -€222
Operating costs €66
Total costs €288
Additional ticket revenues €40
Increased travel time €67
Service reliability effects
- Less waiting time €123
- Reduction in distribution €78
- Increased probability of finding a seat in the vehicle
€4
External effects (emissions, safety, etc.)
€8
Total benefits €336
Benfits-costs +€48
Benfit cost ratio 1,2
Conclusions
In this paper we showed how to calculate the passenger impacts of service variability. We showed that passengers are affected by longer waiting times, more distributed travel times and a reduced probability of having a seat in the vehicle. In the Netherlands, service reliability is not explicitly incorporated in cost benefit analyses, although improved service reliability is often one of the main contributions of public transport projects. In an actual case, the replacement of a bus line by a tram line in Utrecht, we showed that our framework concerning calculating benefits of service reliability is valuable and may be applied directly in practice. By calculating the benefits of the improved service reliability of the proposed tram line, which were substantial, the cost benefit ratio was positive, which convinced the Dutch Minister of Infrastructure and Environment to support the project by €110 million.
References
Ecorys (2011), CBA Uithoflijn, Results report (in Dutch)
Goudappel Coffeng (2011), Demand forecasting and service reliability analysis Uithoflijn Utrecht (in Dutch)
RAND Europe and AVV (2005), The value of reliability in transport: Provisional values for The Netherlands based on expert opinion, Leiden/Rotterdam.
Van Oort, N. (2011), Service Reliability and Urban Public Transport Design, T2011/2, TRAIL PhD Thesis Series, Delft.
