Application of Road Safety Indicators and Inspection Procedures on Existing Urban Intersections. A Dutch Case Study
Giulio Maternini, University of Brescia, Margherita Cadei, University of Brescia, Barbara Zappa, University of Brescia
The paper presents a first methodological proposal for the definition of a road safety indicator which can be applied to evaluate the road safety level of the urban unsignalised intersections through the presentation of a Dutch case study.
Preventive road safety analysis, and in particular, Road Safety Inspections (RSI) are one of the tools that it is possible to apply to assess the safety/quality level of the existing road network. As everybody knows, RSI are considered “preventive procedures” because their goal is to detect safety problems on the existing road network and to propose interventions to solve them by acting before road accidents occur.
The European Directive 2008/96/CE on the road infrastructure safety management gives priority to the application of the RSI procedures to the Trans-European road network, but the application field is going to be progressively extended up to the local urban one.
It is of extreme interest to evaluate the applicability of the inspection procedures also in urban areas: as a matter of fact, compared to the rural ones, urban roads are characterized by a higher level of complexity, due to the presence of traffic components which are generally excluded from the rural road network (i.e. pedestrian and cyclists).
Therefore, it is important to develop specific procedures and, in particular, specific checklists (on which such procedures are based) and indicators, which are able to take into consideration such urban complexity, especially in light of the fact that, so far, researchers mainly concentrated their attention on the RSI procedures carried out on rural roads.
In this direction, the first part of the paper presents the steps which brought to the definition of a checklist valid for a particular kind of urban sites (namely, urban unsignalised intersections between access and distributor roads). Then, the second part aims at proposing a synthetic indicator able to represent the safety level of the observed kind of intersections.
Starting from the review of the Dutch road safety strategies, of the main literature sources and of the available national/international guidelines or manuals, the checklist was developed taking into consideration the most relevant infrastructural factors able to affect the safety of the observed sites.
The checklist has then been applied to different Dutch case studies and the obtained data/results were useful to develop the synthetic safety indicator: each factor has been scored and given a weight by involving a group of road safety experts and by following an analytic hierarchy process, in order to get a synthetic safety value for each intersection.
Highlighting the application field and the scalability of the proposed methodology, the procedure for the validation of the indicator was set, trying to establish a correlation between the indicator and other variables, such as for example the available traffic volumes and road accident data.
From a methodological point of view, the paper tries to emphasise both strong and weak points that characterize the proposed indicator. The quality and availability of data represents, together with the exiguous number of observed sites, the most negative aspects, but at the same time, the developed indicator offers great opportunities. For instance, from an operational point of view, it can be used to establish priorities of intervention or inspection. Alongside this, in terms of future development of the research in this field, it represents the starting point for the development of other checklists (valid, for example, for other kind of urban sites or for other geographic context) and, above all, for the implementation of predictive road accident models, able to estimate the expected frequency of the road accidents.
Association for European Transport