Modeling aggregated accessibility : methodology development and the Aachen Region as a case study

Zheng, Lijuan; Oeser, Markus (Thesis advisor); van Wee, G. P. (Thesis advisor); Scheiner, Joachim (Thesis advisor)

Aachen (2018, 2019)
Dissertation / PhD Thesis

Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2018

Abstract

People need to access a variety of spatially distributed activities (e.g. shopping, working) in their daily life. Accessing these activities is considered as one dimension of quality of life (Karou & Hull, 2014). The accessibility concept usually means the ability to access activities. Improving people's accessibility to activities is the primary aim of transport planning (Derek Halden, 2002). However, conventional transport planning often does not explicitly evaluate accessibility. Conventional transport planning focuses purely on improving the service-level of transport system, which may or may not contribute to the improvement of accessibility. Thus, several authors have emphasized that transport planning should pay more attention to accessibility-based analyses (A. M. El-geneidy & Levinson, 2006; Litman, 2017).Accessibility measures are needed to quantify accessibility. These measures usually include two basic variables. One is the attractiveness of activities, and the other is how travel resistance influences the possibility of conducting trips, which changes with different activity types. For example, people might tolerate longer travel time and travel distance to visit a museum than a supermarket. Hence, when quantifying accessibilities, the different activity types should be distinguished. Correspondingly, the majority of accessibility analyses in the literature quantify accessibility for each specific activity type separately. But what matters for transport planning and land use planning is overall accessibility, which involves all activity types that people need to access in daily life. However, the literature does not provide a clear methodology on how to do this, thus hindering accessibility analyses for real-world application. The objective of this thesis is to develop a model to quantify aggregated accessibility which covers several activity types. Because of our focus on real-world applicability of the methodology, we aim to develop a methodology that can be relatively easily used in practice, based on existing data sources, without conducting any new empirical research. Travel resistance and the way travel resistance influences travel possibility vary among transport modes. For instance, compared to trips on foot, people are less sensitive to travel time for trips by car. Hence, when quantifying accessibility, not only activity types but also transport modes should be distinguished. When generating aggregated accessibilities, we classify activity types into two groups: activities to satisfy fundamental needs and activities to satisfy supplemental needs. The methodology in this thesis consists of three steps to quantify aggregated accessibility. The first step quantifies accessibility of each detailed disaggregated activity type for each transport mode. The second step uses mode split data to combine accessibilities of different transport modes for each activity type, which belongs to one of the two activity groups. The third step develops weighting factors, based on activity types' importance to life, to combine accessibilities of different activity types for each transport mode, and to combine accessibilities, which includes all transport modes, of different activity types. The results of the methodology are accessibility of each activity type for each transport mode, aggregated accessibility of each activity group for each transport mode, and finally aggregated accessibility, which includes all transport modes, of each activity group. This aggregated accessibility model is applied to quantify the aggregated accessibility in the Aachen Region, Germany. This application shows that it is relatively easy to apply the method in a real-world case, based on current data sets, thus, without the need to collect additional data. Contentwise, the results show that the overall accessibility in the two southern cities (Monschau and Simmerath) is significantly lower than the average overall accessibility in the study area, especially the aggregated accessibilities of public transport. A number of policies are proposed to improve the accessibility in Monschau & Simmerath, especially for residents in Monschau & Simmerath who do not have access to car.