Developing an alternative means of assessing speed limits on rural single carriageway roads in Ireland using observed driver behaviour. Bernard C. Sweeney BEng, CEng, MIEI Supervisors: Dr. Tim McCarthy & Dr. Lars Pforte Thesis submitted in fulfilment of the requirements for the degree of Master of Science by Research National Centre for Geocomputation, Faculty of Science Maynooth University, Maynooth, Ireland April 2020 Abstract Speed limits in Ireland have undergone many changes since first introduced, most notably in 2005 when the State adopted metric speed limits. The challenge presented to the Department of Transport, Tourism and Sport and Local Authorities is to assess, manage and implement a system of speed limits that are appropriate, credible, transparent and have the support and respect of the road user. Until 2005 a National Speed Limit applied to all roads outside built-up areas. Metrification then occurred, and the National Speed Limit was replaced by a system of Default Speed Limits that were assigned to each class of road. Over time, this led to a lack of credibility and inconsistency in the speed limit system. This thesis presents a history of how Irish speed limits have evolved and how they are currently set and looks at Ireland’s collision history, its speed limits and its road safety performance in relation to other European countries. Current speed limit assessment methods, both in Ireland and in other jurisdictions, are also presented. An alternative means of assessing the appropriate speed limit for rural single carriageway roads is proposed by deriving a Safe Profile Velocity (Vsp) and an Efficiency Index value for the road or section of road under assessment, by capturing actual driver behaviour - the hypothesis being that the derived Safe Profile Velocity (Vsp) reflects what is occurring on the road and simplifies the assessment method in relation to current methodologies like the Speed Assessment Framework, while retaining core principles. A simplified assessment method is becoming increasingly necessary as Local Authority resources are limited, but demand for a credible speed limit system remains. This thesis contains seven case studies and shows the relationship between the Safe Profile Velocity (Vsp) and existing speed limits - the Efficiency Index, and shows the effect on this Index should the speed limit be altered. The question of considering the use of speed limit values that do not currently exist in legislation also emerges within this thesis. Areas where future analysis or further research may be beneficial are also proposed. i Acknowledgements My sincerest thanks go to Dr. Tim McCarthy and the team, Dr. Lars Pforte, Daire Walsh and Dr. Paul Lewis, for their help and assistance during my work and for the previous work they did on Safe Profile Velocities, which was the catalyst for developing an alternative means to set Speed Limits. Dr. Martin Charlton and Prof. Chris Brunsdon, though they may not have realised it at the time, frequently dropped in nuggets of wisdom and humour that, if not immediately apparent here in this thesis, make their way into some of these pages in some shape or form. I would also like to sincerely thank my Employer, Kildare County Council, who agreed to assist the Department of Transport, Tourism and Sport in the review of the 2010 Special Speed Limit Guidelines and assigned me to that task. In doing so, it fuelled my desire to endeavour to make a tangible contribution to road safety, culminating in my volunteering to undertake research to support that work. Without the support of my Employer, colleagues and the DTTAS Support Office team, this thesis would not have been possible, as it came at a time when resources were tight, and workloads were intensifying. I would also like to thank the Department of Transport, Tourism and Sport for supporting this work. If it were not for my parents, I wouldn’t be here writing this, and I would like to thank them for their tremendous support through University, I will never be able to thank them both enough. I’m sorry Dad that you didn’t get to see the finished product. Finally, I cannot fail to mention the love, encouragement and support I received from my wife, Ciara. Her inquisitive mind and attention to detail and ability to bring me back into the correct ‘driving lane’ in my mind helped me remove any doubts I had. Thank You. I promise I’ll tidy up now and we can have our house back, albeit temporarily...Ellie! ii Contents0B List of Figures ................................................................................................................ v List of Tables ............................................................................................................. viii Chapter 1 - Background & Introduction ....................................................................... 3 1.1 Background .......................................................................................................................... 3 1.2 Introduction ......................................................................................................................... 4 1.3 Methodology ........................................................................................................................ 7 1.4 Case Studies ......................................................................................................................... 7 1.5 Thesis Structure ................................................................................................................... 8 Chapter 2 - Ireland’s Roads and Speed Limits .............................................................. 9 2.1 The Road Network ............................................................................................................. 9 2.1.1 Motorways ............................................................................................................. 10 2.1.2 National Roads ..................................................................................................... 11 2.1.3 Regional Roads ..................................................................................................... 13 2.1.4 Local Roads ........................................................................................................... 14 2.2 Ireland’s Speed Limits ...................................................................................................... 17 2.2.1 History ................................................................................................................... 17 2.2.2 Current Structure of Speed Limits ...................................................................... 19 2.2.3 2013 Speed Limit Review ..................................................................................... 20 2.3 Design Parameters ............................................................................................................ 22 2.3.1 Design Speed ........................................................................................................ 22 2.3.2 Factors Affecting Speed ....................................................................................... 23 2.4 Summary ............................................................................................................................. 27 Chapter 3 - Ireland’s Road Safety Performance .......................................................... 29 3.1 Fatalities and Fatal Collisions .......................................................................................... 29 3.2 Collisions Excluding Fatal Collisions ............................................................................. 36 3.3 Fatal Collisions – Excessive Speed as a Contributory Factor..................................... 37 3.4 Summary ............................................................................................................................. 44 Chapter 4 - Comparing Ireland with Europe .............................................................. 45 4.1 Road Safety Performance ................................................................................................... 45 4.2 Speed Limits ........................................................................................................................ 49 4.3 Summary .............................................................................................................................. 54 Chapter 5 - Contemporary Assessment Methodologies .............................................. 55 5.1 Europe - The MASTER Framework ............................................................................. 56 5.2 The United Kingdom ....................................................................................................... 57 5.3 The Irish Approach .......................................................................................................... 59 5.4 The United States .............................................................................................................. 60 5.5 Summary ............................................................................................................................. 62 iii Chapter 6 - Proposed Methodology and Case Studies ................................................ 67 6.1 Introduction ....................................................................................................................... 67 6.2 Empirical Modelling - Deriving Vsp ...............................................................................