A New Micro-simulation Approach to Model the Impacts of Bus and Traffic Incidents on Bus Performance - the Bus Operators' Perspective
P Polyviou, University of Southampton, UK
In order to detect the fundamental role of bus and traffic related incidents in bus-based public transport, a microscopic simulation model capable of modelling these incidents has been developed and applied to a variety of scenarios.
Mobility is an expression of freedom, an integral part of modern society and part of our culture. However, rapidly increasing traffic resulting mainly from the over-dependence on private cars endangers the cultural heritage and environmental well-being of European cities and limits both freedom of mobility and quality of life. In the attempt to support the use of sustainable transport and increase public transport patronage, bus operations throughout the world are increasingly being equipped with Intelligent Transport Systems (ITS). ITS can support a variety of functions, including Dynamic Bus Fleet Management (DBFM) which has yet to be established in most bus fleets in Europe in a systematic way. According to the UK Sustainable Development Commission (SDC), 84% of total trips in UK are journeys of less than 10 miles, indicating the huge potential for public transport use. Buses are the most dominant mode of public transport, representing 64% of total passenger journeys on public transport in England. Average rating for overall satisfaction for bus services in England was 82 points out of 100 in 2009, unchanged from 2008, indicating that passengers' expectations of bus operations may not be fully met.
In order to detect the fundamental role of bus and traffic related incidents in bus-based public transport for DBFM purposes and aid decision-making in bus operations, a microscopic simulation model capable of modelling these incidents has been developed and applied to a variety of scenarios. This paper describes that literature lacks a commercially available simulation model capable of modelling bus and traffic incidents and their impact on bus operations for bus fleet management purposes. It describes the design and development of the model 'SIBUFEM', for modelling bus operations during whole day periods in which incidents of different types can occur. Data were collected through direct liaising with operators of bus companies such as 'London United' and 'First Bus' in Southampton and SIBUFEM has been applied to a main bus corridor in Southampton, UK, which historically has strong levels of bus use, although this has changed little overall for many years. The paper demonstrates the model's functionality, including the continuous circulation of buses along a bus route, the use of journey time profiles, passenger-dependent bus stop dwell times and deterministic time-dependent queuing theory. Incidents vary from bus breakdowns, to traffic incidents such as road-works, traffic accidents and illegal parking; in SIBUFEM they are specified in terms of their location, duration and severity (loss of capacity). A base case of 'normal' operations has been established and compared with model results from a number of incident scenarios.
The paper presents results showing, for example, the extent to which passenger waiting times increase with increasing incident severity and duration. Results focus on key bus performance measures such as bus journey times, passenger waiting times and bus delays resulting from the incidents. Furthermore, a detailed analysis of the time period while the incident takes place is presented to complete the study of the incident's impacts on the performance indicators and to demonstrate how the effect is greater when the incident occurs in the middle of the bus route than when it occurs at the end of the route. The paper contributes bus related information, such as passenger waiting times, which are particularly useful to transit managers, transport planners, schedulers and the general public, to support DBFM as an innovative ITS application. It shows how to address traffic incidents affecting bus operations promptly and accurately and which control actions are to be taken in a timely and efficient manner so as bus passenger satisfaction should rise, consequently driving an increase in bus use thereby contributing to the sustainability of public transport system.
Association for European Transport