The Development of a Multi-Faceted Evaluation Framework of Shared Spaces

Abstract

The shared space concept is one of many street design approaches that have been innovated in response to the societal realisation of the social and environment impacts of decades of planning and design for the priority of motor vehicles. Utilising road space as a place for social activity is considered a key driver to transform a conventional street to a shared space in a city centre, coupled with an aim to design a public street in such a way that its physical environment influences road user behaviour by reducing vehicular dominance and enhancing pedestrian priority and amenity. These aims form the key objectives when implementing urban shared spaces, together with a desire to improve road safety and economic vitality of the adjoining private land uses. The previous Auckland City Council embraced the road user integration concept by drawing upon international design experience under a 10-year streetscape improvement programme. Several shared space schemes were implemented in the city centre and completed just before the Rugby World Cup 2011 international event. With support from Auckland Transport, a regional transport authority, and in recognition of a need for better understanding of shared space design and operation, particularly to suit the New Zealand context, this research project has developed a methodological framework to thoroughly evaluate the performance of public urban streets based on the qualitative and quantitative data collection from the three case studies of the Elliott, Lorne and Fort Street areas. As part of the literature review process, the research work challenged the view observed by many shared space advocates and practitioners on two counts; one is that the traffic engineering profession is solely responsible for the widespread automobile-centric street environment without much consideration of other street functions. The other is that the road user integration concept was first put into practice by Hans Monderman in the European Shared Space project around the turn of the twenty-first century. The review findings reconnected the Traffic in Towns and the Woonerf idea with the modern shared space concepts and redefined the definition of a shared space to highlight the importance of a consistently low speed environment and multi-functions of a public street, particularly the place function. The identification of the Place, Mobility and Access functions of an urban street contributed to the establishment of five shared space objectives and corresponding key performance indicators. The performance of a shared space was then determined based on how successfully the public space met the objectives relating to Place, Pedestrian, Vehicle, Economic and Safety. Quantitatively, the video records for four consecutive years provided a comprehensive before (2010) and after (2011-2013) data set of user behaviour and interaction. These, coupled with traffic tube counters and crash analysis database formed the main sources for data analysis and comparison. The before (2010) and after (2011) scenario comparison of quantitative performance measures revealed an improved street environment for pedestrians with reduced vehicular dominance (both speeds and volumes) due to the shared space implementation across the three sites. A strong inverse relationship (R2= 0.87) was observed between the normalised pedestrian density and the mean vehicular speed for the Elliott Street section indicating the importance of active land use frontage to the successful operation of a shared space. This research developed a new safety analysis method of the Road User Interaction and Conflict Analysis (RUICS) to assess safety performance. Contrary to the conventional idea of traffic event continuum, where interaction (potential conflict) is an indication of a potential crash, the findings of the RUICS analysis of the before (2010) and after (2011 & 2012) data from the Elliott Street site pointed out that the more user interactions in a shared space, the lower vehicle speeds (R2= 0.81), thereby resulting in less likelihood of injury or fatal crashes in the event of a crash. Qualitatively, the Median Perception Ratings (MPR) of the three CBD case studies were obtained from the on-street perception surveys. With positive MPR values for all three sites, the shared spaces demonstrated that they perform well across the five key performance objectives, especially in comparison to the control site. The on-street surveys along with the semi-structured interviews with urban design and transport professionals, undertaken in 2013, revealed an insight into the qualitative performance characteristics and important evaluation factors of the shared street spaces. The context-sensitive and selfregulating design was also highlighted in the expert interviews, together with the interconnectivity between the five performance measures. The Analytical Hierarchy Process (AHP) was implemented to analyse the 2013 data of the quantitative and qualitative performance measures to obtain a performance index for the three case studies. The relative and global weights of the AHP criteria (shared space objectives) and subcriteria (key performance indicators) have been determined from pairwise comparisons, and sensitivity tested for reliability in producing the final outcomes. A high degree of association between the two quantitative and qualitative AHP models was observed, indicating an ability of the evaluation framework to predict both objective and subjective performance measures. In the end, the Elliott Street area had the highest quantitative performance index of 0.691 (out of 1.0), reflecting the importance of pedestrian activities and interactions, lower vehicle operating speeds and active land-use frontage for successful shared space operation. This doctoral research resulted in four journal articles, six conference papers and one memorandum of shared space design principles for Auckland Transport. The contents of Chapters Six and Seven in this thesis are planned to be submitted for journal publication. Key words: shared space, shared street, urban street space, performance evaluation, performance index, Analytical Hierarchy Process, AHP