Heterogeneous values of time in a multi-modal context: An activity and agent-based simulation approach

Addressing divergent mobility and transportation needs of growing, highly diverse urban population in modern cities is a major challenge for transportation planners and policy makers. Thereby, the heterogeneity of user preferences and needs plays a crucial role in design and evaluation of infrastructure projects and policy measures. Significant share of variations between travellers’ preferences can be captured by heterogeneous distributions of value of travel time savings (VTTS) and schedule delay cost (Small and Verhoef, 2007). VTTS includes the opportunity cost of time and is often regarded to have strong correlation with individuals or households income, but can also vary with travel conditions, trip characteristics or other personal preferences. Schedule delay cost is associated with the time difference between preferred arrival or departure and actual arrival or departure time at or from an activity. Thereby three ways of modelling schedule delay cost have been recently considered in the literature, defined by relationships between value of time and cost of being late to an activity and being early (van den Berg, 2014). In practice, as e.g. in case of work activity, interdependencies between these three parameters result from individual’s profession, flexibility of working hours or type of prevailing work arrangements. Accounting for the multiple dimensions and sources of heterogeneity is a challenging task, bringing analytical approaches and aggregated demand models to its limits. In particular in context of the real world scenarios involving cities with populations of several million people, multimodal transport systems, advanced pricing policies and mixed-used building topology, analytical approach struggles to provide the level of detail and accuracy desired by planners and policy makers. However taking heterogeneity into account in economic project and policy appraisal is essential for an adequate project and policy evaluation. Among many others Arnott et al. (1988), Bates (1996) and van den Berg and Verhoef (2011) find that type and extent of heterogeneity strongly influence welfare effects of congestion tolling and forcefully argue for the need to include it in the models with trip-timing choice. An agent-based modelling approach, widely discussed in the literature, represents a promising alternative to address the challenges associated with travellers’ heterogeneity. Operating on the level of individuals, with attached socio-economic and demographic characteristics, it inherently provides the necessary structure for accounting for personal user preferences. This paper, presents a theoretical framework for inclusion of value of time heterogeneity and 3 types of schedule delay heterogeneity into an agent-based modelling and simulation framework MATSim ( www.matsim.org ). Implications of heterogeneous user preferences are studied and compared with homogeneous population base case as well as the classical transportation economics theory. Based on a multi-modal corridor scenario, implementation of following heterogeneity types is presented and there implications are considered: - interpersonal variations of value of time and money due to the socio-economic characteristics of a household, as in particular household income or how the impact of population heterogeneity, - utility variations between activity types and time of day the activity is performed (different utilities for home and work activity as well as different utilities of morning and evening home activities), - three types of schedule delay heterogeneity: proportional, alpha and gamma heterogeneity as also considered by van den Berg (2014), - heterogeneity in preferred activity start times. Recently Li et al. 2014 used an activity-based approach to incorporate commuters’ day-long activity schedule and time decisions into the Vikrey's bottleneck model for the morning and evening trips and analytically explore the special case of constant marginal utilities. The here presented appraoch goes a step farther and incorporates following models and behavioural characteristics: - non-linear activity utility functions (Charypar and Nagel, 2005), - realistic income distribution based on the synthetic population presented by Chakirov and Fourie (2014), - full day “home – work – home” activity chain and therefore incorporation of schedule dynamics and interdependencies between morning and evening commute, - spatial distribution of home and work locations among either ends of the corridor and therefore heterogeneity in trip distances A 20km long multimodal corridor with bus line running in both directions and with regularly placed bus stops (600m distance) serves as a test scenario. A fully integrated simulation of private and public transport allows accurate accounting for congestion dynamics and road interaction between the two modes. Furthermore, simulation of bus boarding and alighting dynamics using dwell timings depended on vehicle occupancy (Sun et al., 2014) ensures capturing of demand dependent effects as e.g. bus bunching. Initial results are in line with the findings from studies using analytical approaches as e.g. de Palma and Lindsey (2002) and van den Berg and Verhoef (2011) and confirm the necessity of accounting for the heterogeneous user preferences in economic project appraisal. Incorporating heterogeneity into the model significantly changes departure time choice and therewith travel and activity durations as well as social welfare. Furthermore, increase in user heterogeneity shows more efficient modal split and increased use of public transportation. Also differences in types of schedule delay heterogeneity exhibit variant effects of departure time distribution for different income groups. References Arnott, R. , A. de Palma and R. 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