En route to safer roads En route to safer roads How road structure and road classification can affect road safety ISBN: 978-90-73946-08-8 Atze Dijkstra Atze Dijkstra EN ROUTE TO SAFER ROADS How road structure and road classification can affect road safety Atze Dijkstra Promotiecommissie: Voorzitter, secretaris Prof. dr. ir. T.A. Veldkamp Universiteit Twente Promotor: Prof. dr. ir. M.F.A.M. van Maarseveen Universiteit Twente Leden: Prof. dr. ir. E.C. van Berkum Universiteit Twente Prof. dr. J.A. van Zevenbergen Universiteit Twente Prof. ir. F.C.M. Wegman Technische Universiteit Delft Prof. dr. G. Wets Universiteit Hasselt Referent: Dr. M.H.P. Zuidgeest Universiteit Twente SWOV‐Dissertatiereeks, Leidschendam, Nederland. ITC Dissertatie 185 Dit proefschrift is mede tot stand gekomen met steun van de Stichting Wetenschappelijk Onderzoek Verkeersveiligheid SWOV. Het beschreven onderzoek is medegefinancierd door Transumo en door de Europese Unie (zesde kaderprogramma). Uitgever: Stichting Wetenschappelijk Onderzoek Verkeersveiligheid SWOV Postbus 1090 2262 AR Leidschendam E: [email protected] I: www.swov.nl ISBN: 978‐90‐73946‐08‐8 © 2011 Atze Dijkstra Omslagfoto: Theo Janssen Fotowerken Alle rechten zijn voorbehouden. Niets uit deze uitgave mag worden verveelvoudigd, opgeslagen of openbaar gemaakt op welke wijze dan ook zonder voorafgaande schriftelijke toestemming van de auteur. EN ROUTE TO SAFER ROADS HOW ROAD STRUCTURE AND ROAD CLASSIFICATION CAN AFFECT ROAD SAFETY PROEFSCHRIFT ter verkrijging van de graad van doctor aan de Universiteit Twente op gezag van de rector magnificus, prof. dr. H. Brinksma, volgens besluit van het College voor Promoties In het openbaar te verdedigen Op donderdag 12 mei 2011 om 14.45 uur door ATZE DIJKSTRA geboren op 19 november 1954 te Groningen Dit proefschrift is goedgekeurd door de promotor: Prof. dr. ir. M.F.A.M. van Maarseveen Preface In the eighties I conducted a literature survey on the interaction between urban planning, road design and road safety. Many years later, I again broached this topic as part of the ʹSafer Transportation Network Planningʹ project (a co‐operation between the SWOV and a Canadian Insurance company). In both projects it appeared to be difficult to show a (quantitative) relationship between the planning level and the crashes at an operational level. Also the relationship between road network structure and road safety was difficult quantifying. Furthermore, the Dutch concept of Sustainable Safety requires that the fastest route should coincide with the safest route, another aspect demanding further research. In order to elaborate the issues regarding urban planning, road network structure, route choice, and road safety, I proposed a long‐term study ʹRoute choice in road networksʹ. In this project I thought it would be possible to quantify the interactions between these factors by using a simulation model. This would lead me and my fellow colleagues at the SWOV into the world of micro simulation. The study was initially (in the year 2002) going to be carried out by one of my junior colleagues. However, that colleague quite unexpectedly decided to leave SWOV. I had to try and find a replacement, preferably a PhD student. Finding one in the short term was not possible. To compound the problem, my research theme ʹRoad design and road safetyʹ was nearing the end of its four year term and a replacement research subject had not yet started. Combining the two ʹvacanciesʹ (both researcher and subject), resulted in the decision to do the project myself, and thereby taking the first steps towards my PhD project. A review of professors active in the field covered by my project, led me to Martin van Maarseveen as the most promising supervisor. Despite the only relatively large distance between the university in Enschede and the SWOV institute in Leidschendam, a good working relationship was soon established. Although it took some time to get used to each other, we ended up co‐operating well. Martin is very diplomatic and provides input in a very subtle way. This requires listening carefully! The study started with an inventory of models that could be useful for our approach. Luc Wismans (consultant at Goudappel Coffeng) was very helpful in providing us with information about this topic. The next step was to choose a micro simulation model. Ronnie Poorterman (consultant at Grontmij) was the first in offering us the S‐Paramics model for research purposes. Hans Drolenga (at first as an MSc student, later on as a researcher) managed to make that model appropriate for our study; resulting in our first joint TRB paper. Vincent Kars has gradually improved the application that transforms the output from the model into different types of safety indicators. I would also like to acknowledge and thank the many researchers that have worked on parts of the study: Charles Goldenbeld, Robert Louwerse, Peter Morsink, Paula Marchesini (at first as an MSc student), Wendy Weijermars, Frits Bijleveld, and Jacques Commandeur. Also the following (MSc and BSc) students were involved: Marcel Bus, Leander Hepp, Alex Smits, and last but not least, Tjesco Gerts. Marijke Tros patiently carried me through the many layout issues. The individual and combined efforts of these colleagues have resulted in the overall success of this study. My thanks also go to Rob Eenink, my departmental manager. Due to his insight and belief in the importance of micro‐simulation models for research purposes, he could support me practically and keep me alert all through the study. Almost thirty years after graduating as an engineer, and being a researcher from that time on, I will finally be an ʹofficialʹ researcher. Fortunately my employer facilitated this work to a large extent, through which ʹfamily lifeʹ did not suffer too much. Fortunately the family gradually got used to a husband/father working on a PhD thesis. However, the time to spend on our holidays was reduced considerably, something I hope to make up for in the coming years. Table of contents 1. Subject description 11 1.1. Research questions 12 1.2. Subjects of this study 14 2. Characteristics of transportation networks and road networks 19 2.1. Literature review 21 2.2. Criteria for evaluating (road) networks 30 2.3. Summary 31 3. Road network structure and road classification 32 3.1. Functionality of roads 32 3.2. Homogeneity of traffic within a road class 43 3.3. Summary 44 4. Route choice in road networks 45 4.1. Route choice as part of Sustainable Safety 45 4.2. Route choice in general 46 4.3. Navigation systems 55 4.4. Conclusions 57 5. Road safety aspects of road network structure and road classification 59 5.1. Network structure and travel behaviour related to crash numbers 60 5.2. Relating characteristics of network structure, degree of access, road classification and road design to traffic volumes 62 5.3. Relating characteristics of network structure, degree of access, road classification and road design to crash figures 67 5.4. Conclusions 72 6. Detecting the effects of changes in route choice on road safety 74 6.1. Methodological issues 74 6.2. Route criteria, route scores and route stars 90 6.3. Retrieving conflicts from micro‐simulation models 98 6.4. Other conflict based indicators 102 7. Quantitative relationships between calculated conflicts and recorded crashes 109 7.1. Descriptions of the study area and the micro‐simulation model 109 7.2. Conflicts and crashes 111 7.3. Conclusions and recommendations 120 8. Quantitative relationships between route criteria, calculated conflicts, and travel time 122 8.1. Examples of applying DV scores to the study area 122 8.2. Approach, methodological issues and description of data 132 8.3. Analysing scores, numbers of conflicts, and travel times 139 8.4. Conclusions 155 9. Integrated network design 156 9.1. Integrated network design for improving road safety 156 9.2. Designing a road network that is inherently safe 161 9.3. Analysing the network of the study area 164 9.4. Conclusions and recommendations 170 10. Adapting the network structure to improve safety 176 10.1. Route choice in S‐Paramics 176 10.2. Simulations and analyses 182 10.3. Conclusions and recommendations 192 11. A safe mixture of network structure, traffic circulation and route choice 194 11.1. From network structure to safety indicators 194 11.2. Network Safety Procedure 196 12. Conclusions, discussion, recommendations 199 12.1. Conclusions 199 12.2. Discussion and reflection 203 12.3. Recommendations 204 References 207 Appendix A. Traffic circulation systems 217 Appendix B. Distribution of conflict scores 222 Appendix C. Examples of integrated network design 224 Appendix D. Selected nodes 229 Summary 233 Samenvatting 237 Curriculum Vitae 243 SWOV‐Dissertatiereeks 245 1. Subject description The subject of this study is about the influence of network structure and road classification on road safety. Road safety, or unsafety, is usually expressed as the number of crashes or casualties. It is not evident how one can relate what happens at street level to the decisions regarding network design and the elaboration of this design. Traffic circulation can be regarded as the link between these two levels. Behind traffic circulation is the individual who decides to travel from a point of origin to a destination, using a particular route. The route is the starting point for this study. That is because network structure and road classification are important preconditions for traffic circulation and route choice, while the intersecting routes will determine the crash locations. This study will therefore focus on the effects of changing route choices on road safety. The changes in route choice may be the result of: 1. (intended) changes in the structure of the road network 2. a change in traffic circulation, e.g. on account of an alteration of a traffic signal system or of congestion on the main roads 3.