The frequency of natural disasters is increasing all over the world, which can cause immense damage to road infrastructure and its functionality. Therefore, it is crucial to consider the functionality of critical road infrastructure before, during, and after a disaster. For that, global road network data, which is usable for routing applications, is required. OpenStreetMap (OSM) provides global, crowd-sourced road network data that is free and accessible for everyone. However, the usability for routing applications is often an issue. Two main gaps in related studies are identified: the intrinsic improvement of certain aspects of OSM road data for navigational purposes, and missing approaches for the assessment of critical road infrastructure in disaster cases that can handle limited global data availability. Therefore, the aim of this thesis is to develop a generic, multi-scale concept to assess critical road infrastructure in a disaster context using OSM data. For this main objective, two consecutive research goals are identified: (i) improving the routability of OSM data intrinsically, and (ii) assessing critical road infrastructure in a disaster context. Therefore, this thesis and the developed concept are divided into two main parts, each addressing one research goal.
In the first part of this thesis, the OSM road network data is enhanced by improving its routability. The quality of the OSM road network is analyzed in detail, which leads to the identification of two major challenges for the applicability of OSM data in routing applications: missing speed information and road classification errors. To address the first challenge, a Fuzzy Framework for Speed Estimation (Fuzzy-FSE) is developed that employs fuzzy control to estimate average speed based on the parameters road class, road slope, road surface, and link length. The Fuzzy-FSE consists of two parts: a rule and knowledge base, which decides on the output membership functions, and multiple Fuzzy Control Systems, which calculate the output average speeds. Results demonstrate that even using only OSM data, the Fuzzy-FSE performs better than existing methods such as fixed speed profiles. The second challenge of road classification errors is addressed by developing a novel approach to detect road classification errors in OSM by searching for disconnected parts and gaps in different levels of a hierarchical road network. Different parameters are combined in a rating system to obtain an error probability. The rating system can then suggest possible misclassifications to a human user. The results indicate that more classification errors are found at gaps than at disconnected parts. Furthermore, the gap search enables the user to find classification errors quickly using the developed rating system that indicates an error probability. An enhanced OSM road network dataset results from the first part of this thesis.
In the second part of this thesis, the enhanced OSM data is applied to assess critical road infrastructure in a disaster context. The second part of the generic, multi-scale concept is developed, which consists of multiple, interconnected modules. One module implements two accessibility indices, which highlight different aspects of road network accessibility. A basic travel demand model is developed in another module, which estimates daily intercity traffic solely based on OSM data. A third module uses the above-described modules to estimate different natural disaster impacts on the road network. Finally, the vulnerability of the road network towards further disruptions during long-term disasters is analyzed in a fourth module. The generic concept with all modules is applied exemplarily in two different case study regions for two wildfire scenarios. As a result, the concept provides a valuable, flexible, and data-sparse decision aid tool for regional planners and disaster management that can be applied globally and enables country- or region-specific adaptations.