Examining road safety impacts of Green Light Optimal Speed Advisory (GLOSA) system.

Mobility and environmental benefits of Green Light Optimal Speed Advisory (GLOSA) systems have been reported by many previous research studies, however, there is insufficient knowledge on the safety implications of such an application. For safe deployment of GLOSA system, it is most critical to identify and address potential safety issues in the design process. It can be argued that implementation of GLOSA system can improve safety by reducing traffic conflicts associated with the interrupted traffic flow at signalised intersections. However, more research findings are needed from field and simulation based studies to evaluate the impacts on safety under a variety of real-world scenarios. As part of the LEVITATE (Societal Level Impacts of Connected and Automated Vehicles) project under European Union's Horizon 2020 Programme, the main objective of this study is to examine the safety impacts of GLOSA under mixed traffic compositions with varying market penetration rates (MPR) of connected and automated vehicles (CAVs). A calibrated and validated microsimulation model (developed in Aimsun) of the greater Manchester area was used for this study where three signalised intersections in a corridor were identified for implementing GLOSA system. An improved algorithm was developed by identifying the potential issues/limitations in some of the GLOSA algorithms found in literature. Behaviours of CAVs were modelled based on the findings of a comprehensive literature review. Safety analysis was performed through processing the simulated vehicular trajectories in the surrogate safety assessment model (SSAM) by the Federal Highway Administration (FHWA). The surrogate safety assessment results showed small improvement in safety with the GLOSA implementation at multiple intersections in the test network only at low MPR (20%) scenarios of CAVs, as compared to the respective without GLOSA scenarios. No or rather slightly lower improvement in safety was observed with GLOSA implementation under mixed fleet scenarios with 40 % or higher 1st Generation or 2nd Generation CAVs, as compared to the respective scenarios without GLOSA. The implementation of GLOSA system was also found to have some impact on the traffic conflict types (although not consistent across all MPR scenarios), where rear-end conflicts were found to decrease while a slight increase was observed in lane-change conflicts.

Network-wide safety impacts of dedicated lanes for connected and autonomous vehicles.

Cooperative, Connected and Automated Mobility (CCAM) enabled by Connected and Autonomous Vehicles (CAVs) has potential to change future transport systems. The findings from previous studies suggest that these technologies will improve traffic flow, reduce travel time and delays. Furthermore, these CAVs will be safer compared to existing vehicles. As these vehicles may have the ability to travel at a higher speed and with shorter headways, it has been argued that infrastructure-based measures are required to optimise traffic flow and road user comfort. One of these measures is the use of a dedicated lane for CAVs on urban highways and arterials and constitutes the focus of this research. As the potential impact on safety is unclear, the present study aims to evaluate the safety impacts of dedicated lanes for CAVs. A calibrated and validated microsimulation model developed in AIMSUN was used to simulate and produce safety results. These results were analysed with the help of the Surrogate Safety Assessment Model (SSAM). The model includes human-driven vehicles (HDVs), 1st generation and 2nd generation autonomous vehicles (AVs) with different sets of parameters leading to different movement behaviour. The model uses a variety of cases in which a dedicated lane is provided at different type of lanes (inner and outer) of highways to understand the safety effects. The model also tries to understand the minimum required market penetration rate (MPR) of CAVs for a better movement of traffic on dedicated lanes. It was observed in the models that although at low penetration rates of CAVs (around 20%) dedicated lanes might not be advantageous, a reduction of 53% to 58% in traffic conflicts is achieved with the introduction of dedicated lanes in high CAV MPRs. In addition, traffic crashes estimated from traffic conflicts are reduced up to 48% with the CAVs. The simulation results revealed that with dedicated lane, the combination of 40-40-20 (i.e., 40% human-driven - 40% 1st generation AVs- 20% 2nd generation AVs) could be the optimum MPR for CAVs to achieve the best safety benefits. The findings in this study provide useful insight into the safety impacts of dedicated lanes for CAVs and could be used to develop a policy support tool for local authorities and practitioners.

A comprehensive analysis of the relationships between the built environment and traffic safety in the Dutch urban areas.

Built-environment factors potentially alleviate or aggravate traffic safety problems in urban areas. This paper aims to investigate the relationships of these factors with vehicle-bicycle and vehicle-vehicle property damage only (PDO) and killed and severe injury (KSI) crashes in urban areas. For this purpose, an area-level analysis using 100x100m2 cells, along with a Spatial Hurdle Negative Binomial regression model were employed. The study area is composed of a selection of municipalities in the Netherlands-Randstad Area where major land-use developments have occurred since the 1970s. The study was conducted by developing a rich dataset composed of various national and local databases. The findings reveal that built-environment factors and land-use policies have substantial impacts on safety, which cannot be neglected. The factors explaining the land-use density and diversity in the area (e.g., urbanity and function mixing levels), as well as the land-use design characteristics (indicated by average age of the neighborhoods), traffic and road network characteristics, and proximity to different destinations influence the probability, frequency, and severity of crashes in urban areas. Furthermore, low socioeconomic levels are associated with a higher frequency of traffic crashes.

First steps towards a holistic impact assessment methodology for connected and automated vehicles.

Connected and automated vehicles have become more common in recent years, increasing the need to assess their societal level impacts. In this paper a methodology is presented to explore and define relevant impact areas as a starting point for quantitative impact assessment. The many interrelations between impact areas increases the complexity of obtaining a complete overview. Therefore, a structured approach is used, which shows many similarities with the modelling of causal-loop-diagrams. Feedback loops between impact areas are taken into account at an early stage and methods of literature research, project team feedback, interrelation assessment and grouping are used to produce a holistic overview of impacts. The methodology was developed and applied in the European H2020 project LEVITATE. The impact taxonomy and interrelations between impact areas resulting from this project are presented and further steps needed to perform a quantitative evaluation of the impacts are discussed.

A systematic cost-benefit analysis of 29 road safety measures.

Economic evaluations of road safety measures are only rarely published in the scholarly literature. We collected and (re-)analyzed evidence in order to conduct cost-benefit analyses (CBAs) for 29 road safety measures. The information on crash costs was based on data from a survey in European countries. We applied a systematic procedure including corrections for inflation and Purchasing Power Parity in order to express all the monetary information in the same units (EUR, 2015). Cost-benefit analyses were done for measures with favorable estimated effects on road safety and for which relevant information on costs could be found. Results were assessed in terms of benefit-to-cost ratios and net present value. In order to account for some uncertainties, we carried out sensitivity analyses based on varying assumptions for costs of measures and measure effectiveness. Moreover we defined some combinations used as best case and worst case scenarios. In the best estimate scenario, 25 measures turn out to be cost-effective. 4 measures (road lighting, automatic barriers installation, area wide traffic calming and mandatory eyesight tests) are not cost-effective according to this scenario. In total, 14 measures remain cost-effective throughout all scenarios, whereas 10 other measures switch from cost-effective in the best case scenario to not cost-effective in the worst case scenario. For three measures insufficient information is available to calculate all scenarios. Two measures (automatic barriers installation and area wide traffic calming) even in the best case do not become cost-effective. Inherent uncertainties tend to be present in the underlying data on costs of measures, effects and target groups. Results of CBAs are not necessarily generally valid or directly transferable to other settings.

The European road safety decision support system on risks and measures.

The European Road Safety Decision Support System (roadsafety-dss.eu) is an innovative system providing the available evidence on a broad range of road risks and possible countermeasures. This paper describes the scientific basis of the DSS. The structure underlying the DSS consists of (1) a taxonomy identifying risk factors and measures and linking them to each other, (2) a repository of studies, and (3) synopses summarizing the effects estimated in the literature for each risk factor and measure, and (4) an economic efficiency evaluation instrument (E3-calculator). The DSS is implemented in a modern web-based tool with a highly ergonomic interface, allowing users to get a quick overview or go deeper into the results of single studies according to their own needs.

Burden of injury of serious road injuries in six EU countries.

BACKGROUND: Information about the burden of (non-fatal) road traffic injury is very useful to further improve road safety policy. Previous studies calculated the burden of injury in individual countries. This paper estimates and compares the burden of non-fatal serious road traffic injuries in six EU countries/regions: Austria, Belgium, England, The Netherlands, the Rhône region in France and Spain. METHODS: It is a cross-sectional study based on hospital discharge databases. POPULATION: of study are patients hospitalized with MAIS3+ due to road traffic injuries. The burden of injury (expressed in years lived with disability (YLD)) is calculated applying a method that is developed within the INTEGRIS study. The method assigns estimated disability information to the casualties using the EUROCOST injury classification. RESULTS: The average burden per MAIS3+ casualty varies between 2.4 YLD and 3.2 YLD per casualty. About 90% of the total burden of injury of MAIS3+ casualties is due to lifelong consequences that are experienced by 19% to 33% of the MAIS3+ casualties. Head injuries, spinal cord injuries and injuries to the lower extremities are responsible for more than 90% of the total burden of MAIS3+ road traffic injuries. Results per transport mode differ between the countries. Differences between countries are mainly due to differences in age distribution and in the distribution over EUROCOST injury groups of the casualties. CONCLUSION: The analyses presented in this paper can support further improvement of road safety policy. Countermeasures could for example be focused at reducing skull and brain injuries, spinal cord injuries and injuries to the lower extremities, as these injuries are responsible for more than 90% of the total burden of injury of MAIS3+ casualties.

Road injuries, health burden, but not fatalities make 12- to 17-year olds a high risk group in the Netherlands.

Background: To explore the impact of road injuries for different age groups, this study compares the health burden of road injuries in young adolescents-12 to 17 years of age-to those for older age groups. Young adolescents are underrepresented in road fatalities. However, their inexperience, developmental stage and use of bicycles may expose them to high levels of road risk, but their physical resilience may help them survive injuries which in older age groups would be fatal. Methods: To assess the impact of injuries compared with death, this study assessed by age group the health burden expressed in disability adjusted life years; years of life lost plus years lived with disability. Its analyses make use of existing data bases on road fatalities, serious injuries (maximum abbreviated injury score 2 or more), travel, life expectancy and disability weights. Results: For young adolescents, seriously injuries per distance travelled (injury risk) were higher than for any other age group, except for the elderly (75+). This was further amplified when health burden was taken into account, showing these young adolescents to be responsible for 15% of the total health burden associated with road crashes. Conclusions: These results justify extra efforts to improve the understanding and prevention of injury-only crashes among young adolescents.

Serious road injuries in The Netherlands dissected.

OBJECTIVE: This article discusses the characteristics and injury patterns of serious road injuries (Maximum Abbreviated Injury Scale [MAIS] 2+ inpatients) in The Netherlands. METHODS: In The Netherlands, the actual number of serious injuries is estimated by linking police data to hospital data. The distribution of serious road injuries over (1) travel mode and gender and (2) crash type and age are compared for the years 2000 and 2011. Moreover, the distribution of the injuries over the body regions is illustrated using colored injury body profiles. RESULTS: The number of serious injuries is higher for men than for women and increased from 16,500 in 2000 to 19,700 in 2011. In 2011, about half (51%) of the serious road injuries were due to a bicycle crash not involving a motor vehicle. The share of casualties aged 60 years and older is relatively high (43% in 2011) in these crashes. The injury body profiles show that head injuries (31%) and injuries to the lower extremities (37%) are most prevalent. Compared to other travel modes, pedestrians and riders of powered 2-wheelers relatively often sustain lower-leg injuries compared to other travel modes. Head injuries are most prevalent in cyclists who are injured in a crash with a motorized vehicle. Cyclists who are injured in a crash not involving a motor vehicle and casualties of 60 years and older relatively often include hip or upper-leg injuries. CONCLUSION: The characteristics of serious road injuries differ from those of fatalities and the distribution of injuries over the body differs by travel mode, gender, and age.

Burden of road traffic injuries: Disability-adjusted life years in relation to hospitalization and the maximum abbreviated injury scale.

BACKGROUND: The consequences of non-fatal road traffic injuries (RTI) are increasingly adopted by policy makers as an indicator of traffic safety. However, it is not agreed upon which level of severity should be used as cut-off point for assessing road safety performance. Internationally, within road safety, injury severity is assessed by means of the maximum abbreviated injury scale (MAIS). The choice for a severity cut-off point highly influences the measured disease burden of RTI. This paper assesses the burden of RTI in terms of disability adjusted life years (DALYs) by hospitalization status and MAIS cut-off point in the Netherlands. METHODS: Hospital discharge register (HDR) and emergency department (ED) data for RTI in the Netherlands were selected for the years 2007-2009, as well as mortality data. The incidence, years lived with disability (YLD), years of life lost (YLL) owing to premature death, and DALYs were calculated. YLD for admitted patients was subdivided by MAIS severity levels. RESULTS: RTI resulted in 48,500 YLD and 27,900 YLL respectively, amounting to 76,400 DALYs per year in the Netherlands. The largest proportion of DALYs is related to fatalities (37%), followed by admitted MAIS 2 injuries (25%), ED treated injuries (16%) and admitted MAIS 3+ injuries (18%). Admitted MAIS 1 injuries only account for a small fraction of DALYs (4%). In the Netherlands, the diseases burden of RTI is highest among cyclists with 39% of total DALYs. One half of all bicycle related DALYs are attributable to admitted MAIS 2+ injuries, but ED treated injuries also account for a large proportion of DALYs in this group (28%). Car occupants are responsible for 26% of all DALYs, primarily caused by fatalities (66%), followed by admitted MAIS 2+ injuries (25%). ED treated injuries only account for 5% of DALYs in this group. CONCLUSIONS: When using admitted MAIS 3+ or admitted MAIS 2+ as severity cut-off point, 54% and 80% of all DALYs are captured respectively. Assessing the influence of different severity cut-off points by MAIS on the proportion and number of DALYs captured gives valuable information for guiding choices on the definition of serious RTI.

Road safety performance indicators for the interurban road network.

Various road safety performance indicators (SPIs) have been proposed for different road safety research areas, mainly as regards driver behaviour (e.g. seat belt use, alcohol, drugs, etc.) and vehicles (e.g. passive safety); however, no SPIs for the road network and design have been developed. The objective of this research is the development of an SPI for the road network, to be used as a benchmark for cross-region comparisons. The developed SPI essentially makes a comparison of the existing road network to the theoretically required one, defined as one which meets some minimum requirements with respect to road safety. This paper presents a theoretical concept for the determination of this SPI as well as a translation of this theory into a practical method. Also, the method is applied in a number of pilot countries namely the Netherlands, Portugal, Greece and Israel. The results show that the SPI could be efficiently calculated in all countries, despite some differences in the data sources. In general, the calculated overall SPI scores were realistic and ranged from 81 to 94%, with the exception of Greece where the SPI was relatively lower (67%). However, the SPI should be considered as a first attempt to determine the safety level of the road network. The proposed method has some limitations and could be further improved. The paper presents directions for further research to further develop the SPI.