The High-risk intersections guide (HRIG) is a comprehensive assessment framework for evaluating safety at intersections (NZ Transport Agency 2013b). It provides transport professionals with best practice guidelines to identify, target and address key road safety issues at high-risk intersections. However, there is a knowledge gap in identifying why some urban signalised intersections have a higher risk of death and serious injury than others, and the guide does not assist transport professionals in identifying specific methods to improve the safety of urban signalised intersections. The NZ Transport Agency contracted Abley Transportation Consultants to address these knowledge gaps. The purpose of this research project was to qualitatively analyse a number of urban signalised intersections for a range of factors that might influence safety, then disseminate the research findings to assist practitioners in selecting effective safety treatments for urban signalised intersections. Compared with existing statistical approaches for modelling crash risk, this research used a qualitative whole-system approach to identify factors that might normally be missed due, for example, to the random nature of crashes and their severity, or the process of defining variables for mathematical analysis. The research fits with the NZ Transport Agency’s Safe System approach by seeking to identify factors which will lead to safer roads and roadsides. Later chapters focus specifically on death and injury crashes. By researching and identifying factors correlated to these types of crashes, factors can be mitigated or removed leading to a lower risk of death or injury when driver mistakes occur. The specific objectives of the research were: • Identify a wide range of factors relating to increased death and serious injury risk at urban signalised intersections, from New Zealand and international literature. • Select a sample of New Zealand urban signalised intersections that have a higher occurrence of death and serious injury crashes than would be expected, based on the type of intersection and traffic flows, for more detailed analysis. Identify a number of intersections performing in line with expectations and better than expected, to act as control group. • Analyse the sample of intersections in detail, including desktop assessment of crash report information followed by a series of field inspections and technical analysis to qualify effects of the factors identified above upon crash performance (Land Transport NZ 2004). • Document and disseminate the findings of the research to assist practitioners in selecting effective safety treatments for urban signalised intersections. The research underpinning this report was undertaken during 2014–2015, starting with a literature review and concluding with the refinement and finalisation of guidance for specific factors associated with increased crash risk. This report presents both an overview of the research process as it was developed, and the outputs (including recommendations) that were generated. The report is organised as follows:Chapter 2 provides background for the research by summarising the findings of international and New Zealand literature on urban signalised intersections. Factors found to affect crash rates at urban signalised intersections are investigated further in chapters 3 and 4. The key findings from the literature review are also highlighted in the conclusions and recommendations.Chapter 3 describes the analysis of coded factors from CAS for injury crashes occurring at or near several thousand urban signalised intersections. The key crash types and factors influencing crash rates are investigated further in chapter 4 and carried through to the conclusions and recommendations.Chapter 4 describes the analysis of non-coded factors for 40 selected signalised intersections as informed by site visits. The key factors found to influence crash rates are investigated further in chapter 5 using statistical analysis and carried through to the conclusions and recommendations.Chapter 5 describes the statistical analysis of 100 further signalised intersections to determine if there is a statistically significant difference in crash rate between signalised intersections with and without the key factors identified in chapters 3 and 4.Chapter 6 presents additional discussion to conclude the technical assessment including the presentation of a useful resource for practitioners which combines the factors identified in chapter 5 with crash factors from prior research.Chapter 7 presents conclusions and recommendations arising from the research. (Author/publisher)
Samenvatting