Roundabouts are hastily spreading around the world, mainly because of their good safety performance, and several countries have recently updated their standards and guidelines. However, inconsistencies in design standards and practices are observed. In this paper, a critical review of the Australasian, EU, and US standards and guidelines is performed. As a result, key issues of the existing standards are identified, along with research areas to fill the knowledge gaps and recommendations for improvement in a case study, Italy. These recommendations are mainly based on the concepts of design flexibility and performance based design. Indeed, rigid standards, which do not really take into account safety and operational consequences of the design decisions and the need to balance opposing demands, might produce undesirable outcomes.

Purpose: Over the past 10 years, building on road infrastructure data, crash prediction models (CPMs) have become fundamental scientific tools for road safety management. However, there is a gap between state-of-the-art and state-of-the-practice, with the practical application lagging behind scientific progress. This motivated a review of international experience with CPMs from perspectives of application by practitioners and development by researchers. The objective of the paper is to improve practitioner understanding of modelling road safety performance using CPMs for crash frequency estimation, leading to their greater uptake in improving road safety. In short, why and how should road safety practitioners consider CPMs? Methods: Both scientific and practice-oriented literature was retrieved, using academic sources, as well as reports of road agencies or institutes. The selection was limited to English language. Results: From the review it is clear that developing CPMs is not a straightforward task: there are many available choices and decisions to be made during the process without definite guidance. This explains the diversity of approaches, techniques, and model types. The paper explains how some fundamental modelling decisions affect practical aspects of modelling safety performance. Conclusions: There is a need to identify CPM solutions that will be scientifically sound and feasible in practitioners' context. Together with increased communication between researchers and practitioners, these solutions will help overcome the identified challenges and increase use of CPMs.

The paper presents a critical review of the Australasian, EU and US roundabout geometric design standards and guidelines and identifies inconsistencies of the Italian roundabout standard which deserve improvement. As a result, recommendations for improvement of the Italian standard are proposed. These recommendations are mainly based on the concepts of design flexibility and performance based design. Indeed, rigid standards which do not really take into account safety and operational consequences of the design decisions and the need to balance opposite demands might produce undesirable outcomes

Crash data collection is crucial for road safety improvement, but Italy is considerably behind the best international practices. To help to bridge this gap, a critical review of international crash databases was carried out and recommendations for improvement of the Italian police crash data collection and the national crash database were formulated. Main issues identified in the research are related to the database access procedures, the crash report, the crash location, the crash classification, and the severity classification

Because the quality of decision making in road safety is dependent on the quality of the data on which decisions are based, efforts to improve the quality, timeliness, and accuracy of crash databases are crucial. A critical review of Australasian, European Union, and U.S. crash databases was performed, and future directions were identified. Major issues included procedures for access to crash data, crash report forms, severity of crashes reported in the databases, crash locations, crash classification, and crash severity. Access to crash databases could be provided to approved road safety professionals through a web-based portal, which could also provide detailed police crash reports. The use of electronic crash report forms was strongly recommended because it might solve most of the problems associated with paper forms. The severity of crashes reported in the databases varied across countries, and not all countries reported property-damage-only crashes. However, for both prevention and consistency between countries, collecting property-damage-only crash reports and using them to develop safety strategies is recommended. Combined use of Global Positioning System devices and geographic information systems improves the reporting of crash locations and overcomes traditional problems such as inaccuracies and collection mistakes. To develop effective countermeasures, it is recommended that crashes be classified by the maneuvers and sequence of events for each traffic unit. The adoption of the same system for crash severity classification in different countries would allow comparisons in safety performance between countries and jurisdictions.