Identification of infrastructure related risk factors, Deliverable 5.1 of the H2020 project SafetyCube

The present Deliverable (D5.1) describes the identification and evaluation of infrastructure related risk factors. It outlines the results of Task 5.1 of WP5 of SafetyCube, which aimed to identify and evaluate infrastructure related risk factors and related road safety problems by (i) presenting a taxonomy of infrastructure related risks, (ii) identifying “hot topics” of concern for relevant stakeholders and (iii) evaluating the relative importance for road safety outcomes (crash risk, crash frequency and severity etc.) within the scientific literature for each identified risk factor. To help achieve this, Task 5.1 has initially exploited current knowledge (e.g. existing studies) and, where possible, existing accident data (macroscopic and in-depth) in order to identify and rank risk factors related to the road infrastructure. This information will help further on in WP5 to identify countermeasures for addressing these risk factors and finally to undertake an assessment of the effects of these countermeasures. In order to develop a comprehensive taxonomy of road infrastructure-related risks, an overview of infrastructure safety across Europe was undertaken to identify the main types of road infrastructure-related risks, using key resources and publications such as the European Road Safety Observatory (ERSO), The Handbook of Road Safety Measures (Elvik et al., 2009), the iRAP toolkit and the SWOV factsheets, to name a few. The taxonomy developed contained 59 specific risk factors within 16 general risk factors, all within 10 infrastructure elements. In addition to this, stakeholder consultations in the form of a series of workshops were undertaken to prioritise risk factors (‘hot topics’) based on the feedback from the stakeholders on which risk factors they considered to be the most important or most relevant in terms of road infrastructure safety. The stakeholders who attended the workshops had a wide range of backgrounds (e.g. government, industry, research, relevant consumer organisations etc.) and a wide range of interests and knowledge. The identified ‘hot topics’ were ranked in terms of importance (i.e. which would have the greatest effect on road safety). SafetyCube analysis will put the greatest emphasis on these topics (e.g. pedestrian/cyclist safety, crossings, visibility, removing obstacles). To evaluate the scientific literature, a methodology was developed in Work Package 3 of the SafetyCube project. WP5 has applied this methodology to road infrastructure risk factors. This uniformed approach facilitated systematic searching of the scientific literature and consistent evaluation of the evidence for each risk factor. The method included a literature search strategy, a ‘coding template’ to record key data and metadata from individual studies, and guidelines for summarising the findings (Martensen et al, 2016b). The main databases used in the WP5 literature search were Scopus and TRID, with some risk factors utilising additional database searches (e.g. Google Scholar, Science Direct). Studies using crash data were considered highest priority. Where a high number of studies were found, further selection criteria were applied to ensure the best quality studies were included in the analysis (e.g. key meta-analyses, recent studies, country origin, importance). Once the most relevant studies were identified for a risk factor, each study was coded within a template developed in WP3. Information coded for each study included road system element, basic study information, road user group information, study design, measures of exposure, measures of outcomes and types of effects. The information in the coded templates will be included in the relational database developed to serve as the main source (‘back end’) of the Decision Support System (DSS) being developed for SafetyCube. Each risk factor was assigned a secondary coding partner who would carry out the control procedure and would discuss with the primary coding partner any coding issues they had found. Once all studies were coded for a risk factor, a synopsis was created, synthesising the coded studies and outlining the main findings in the form of meta-analyses (where possible) or another type of comprehensive synthesis (e.g. vote-count analysis). Each synopsis consists of three sections: a 2 page summary (including abstract, overview of effects and analysis methods); a scientific overview (short literature synthesis, overview of studies, analysis methods and analysis of the effects) and finally supporting documents (e.g. details of literature search and comparison of available studies in detail, if relevant). To enrich the background information in the synopses, in-depth accident investigation data from a number of sources across Europe (i.e. GIDAS, CARE/CADaS) was sourced. Not all risk factors could be enhanced with this data, but where it was possible, the aim was to provide further information on the type of crash scenarios typically found in collisions where specific infrastructure-related risk factors are present. If present, this data was included in the synopsis for the specific risk factor. After undertaking the literature search and coding of the studies, it was found that for some risk factors, not enough detailed studies could be found to allow a synopsis to be written. Therefore, the revised number of specific risk factors that did have a synopsis written was 37, within 7 infrastructure elements. Nevertheless, the coded studies on the remaining risk factors will be included in the database to be accessible by the interested DSS users. At the start of each synopsis, the risk factor is assigned a colour code, which indicates how important this risk factor is in terms of the amount of evidence demonstrating its impact on road safety in terms of increasing crash risk or severity. The code can either be Red (very clear increased risk), Yellow (probably risky), Grey (unclear results) or Green (probably not risky). In total, eight risk factors were given a Red code (e.g. traffic volume, traffic composition, road surface deficiencies, shoulder deficiencies, workzone length, low curve radius), twenty were given a Yellow code (e.g. secondary crashes, risks associated with road type, narrow lane or median, roadside deficiencies, type of junction, design and visibility at junctions) seven were given a Grey code (e.g. congestion, frost and snow, densely spaced junctions etc.). The specific risk factors given the red code were found to be distributed across a range of infrastructure elements, demonstrating that the greatest risk is spread across several aspects of infrastructure design and traffic control. However, four ‘hot topics’ were rated as being risky, which were ‘small work-zone length’, ‘low curve radius’, ‘absence of shoulder’ and ‘narrow shoulder’. Some limitations were identified. Firstly, because of the method used to attribute colour code, it is in theory possible for a risk factor with a Yellow colour code to have a greater overall magnitude of impact on road safety than a risk factor coded Red. This would occur if studies reported a large impact of a risk factor but without sufficient consistency to allocate a red colour code. Road safety benefits should be expected from implementing measures to mitigate Yellow as well as Red coded infrastructure risks. Secondly, findings may have been limited by both the implemented literature search strategy and the quality of the studies identified, but this was to ensure the studies included were of sufficiently high quality to inform understanding of the risk factor. Finally, due to difficulties of finding relevant studies, it was not possible to evaluate the effects on road safety of all topics listed in the taxonomy. The next task of WP5 is to begin identifying measures that will counter the identified risk factors. Priority will be placed on investigating measures aimed to mitigate the risk factors identified as Red. The priority of risk factors in the Yellow category will depend on why they were assigned to this category and whether or not they are a hot topic

Identification of safety effects of infrastructure related measures, Deliverable 5.2 of the H2020 project SafetyCube

Identification of safety effects of infrastructure related measures, Deliverable 5.2 of the H2020 project SafetyCub

Potential safety applications of advanced technology. Final Report

Notes: Report covers the period Sept 1990 - June 1993. Originally dated June 1993Federal Highway Administration, Office of Safety and Traffic Operations Research and Development, McLean, Va.http://deepblue.lib.umich.edu/bitstream/2027.42/1045/2/85136.0001.001.pd

A Multi-~Procedural Approach to Evaluating Walkability and Pedestrian Safety

Walking has sound health benefits and tends to be a pleasurable experience requiring no fuel, fare, license, nor registration. Whilst walking is recommended as part of physical activity, it is necessary to provide a conducive and safe walking environment. In an effort to determine an optimum combination of infrastructure that would create walkable, transit-oriented neighborhoods eliminating unnecessary motorized trips; various approaches evaluating an assortment of features in the walking environment have been implemented. However, some factors such as crash risk which have an essential contribution to the suitability of the walking environment have yet to be considered. Therefore the objective of this study was to quantify the walking environment, by developing a comprehensive walkability index which reflects the condition of the walking environment as well as pedestrians\u27 perceptions of the walking environment. Developing the walkability index included three sub-objectives as follows: 1. Incorporate crash risk in the development of walkability indices which has not been done in previous walkability studies. An overall safety index was designed to estimate safety in the built environment in a more complete form. 2. Analyze the impact of features in the built walking environment on walking for recreational or utilitarian purposes. The analyses also determined whether sampled residents\u27 perception of their walking facilities is comparable to the objective audit observations in various categories. 3. Identify features in the built environment that influence resident perception of their walking environment. This involved analyzing patterns and relationships between features in the walking environment and resident perceptions. Results would relate resident perceptions and walking environment features using calibrated statistical models. The study methodology included conducting a resident survey, an audit of objectively measured features in the walking environment and a pedestrian safety analysis. The survey collected residents\u27 perceptions of their walking environment expressed using natural language. A perception quality grade of walkability based on resident perceptions was developed from the survey data. An audit of survey neighborhoods was performed by a trained auditor using Google earth, maps, and site visits. Features in the walking environment such as driveways, signals, and crosswalks among others, were measured on a segment by segment basis. Using the various features measured on a segment, an audit quality index for walkability was developed for each neighborhood. A crash index was also developed as a function of population and commercial land use within the survey neighborhoods. The findings of this study are expected to enhance evaluation of walking environments. The safety index incorporating crash risk and objectively measured safety elements provides a more representative indicator of safety levels within the walking environment. In addition, crash data increases objectivity to neighborhood audits depending on how audit scores are estimated. The fuzzy logic approach to estimating resident perceptions of the walking environment enables analysis of imprecise information to obtain logical output through computing with words. As such, residents\u27 opinions which are analyzed in an approximate framework similar to the human ability to manipulate and reason with perceptions are more consistent with initial resident evaluations. With improved walkability estimation, decision makers are better equipped during planning to select appropriate strategies that encourage walking in a safe environment for recreational and utilitarian purposes. Comparison of developed audit quality walkability indices, with and without crash data indicates significant differences in walkability indexes. Neighborhoods with initial high walkability indexes ranked much lower after crash data integration. Even without statistical significance, crash data provides more objectivity to audit quality indexes based on depending on data collection and reduction. The study used multinomial logit to identify parameters that influence walking frequency. Results indicate that land use, and aesthetic and amenities perceptions have a significant relationship with walking frequency. This is intuitive because more varied land uses not only attract more pedestrians, but also provides opportunities for trip chaining. As expected, better aesthetics and amenities and infrastructure are associated with higher walking frequencies. Both aesthetics and amenities and land use perception were correlated with safety, directness and continuity perceptions, implying improving the perception of one category was bound to have an impact on another perception category. The study also used mixed models to identify features in the built environment that influence the multinomial model perceptions that in turn influence walking frequency. Results from the continuity, directness, land use, aesthetics and amenities perception models are as expected. For example, neighborhoods with initial low land use perception are likely to be more sensitive to the presence of new commercial premises (e.g. small convenient store) nearby. However, directness-audit parameter serves as both a disincentive and incentive. To land use perception, increasing directness features results in uninhibited access to land uses which increases walking frequency. Conversely, increase in uninhibited access results in lower safety perception. Intuitively, enclosed communities have lower traffic flows as well as speed limits that are conducive for pedestrian activity as well as providing buffers from traffic. Overall, results indicate the need for a transactional evaluation approach, in which pedestrian behavior is multiply influenced by environmental features, perception of the walking environment, as well as social and cultural aspects

Relating Interface Type, Building Type, Street Type and Local Travel Activity in Taipei

As part of the current trend for sustainable transport systems and for lively cities, considerable research has been conducted into the relationship between urban form and travel activity. Related Taiwanese studies are relatively scarce, however, perhaps because there is a lack of research about Taiwanese urban morphology. Therefore, establishing a complete urban form catalogue (including building type, street type, and interface type in particular) is the first step and prime objective for this thesis to contribute to the omission in the current academia, and further identifying the urban form types with their travel activity characteristics (mostly mode choice and walking behaviour) to recognise which form types are more favourable under the contexts of sustainable and lively lifestyle. Throughout the study, interfaces, i.e. the connections between different urban form components, are given particular focus. This is done firstly because interface is almost entirely undocumented in existing Taiwanese urban morphology, and secondly because, although the transition between the private and public domain is seen as playing a vital role in pedestrian or public life studies, but little discussion about it as an integral factor in most transport related research. This thesis is based on the study of both the physical fabric and residents’ travel activity pattern of Da-An District. Therefore, a two-dimensional coordinate system (x-y matrix) and cluster methods (e.g. K-Means) were used to classify the urban form types, whilst a questionnaire was used to gain the travel activity data. As a result, the urban form of the selected study area was found to comprise 10 building types, 12 street types, and 24 interface types. Through Chi-square tests, certain street and interface types were then found to be associated with certain transport mode shares for local trips. A number of specific interface types were further recognised as favourable (e.g. arcades with shop windows, and large landscaped front setbacks) or unfavourable (e.g. overhang without setback) to a sustainable and lively environment

Hardware-in-the-Loop Simulation to Evaluate the Performance and Constraints of the Red-light Violation Warning Application on Arterial Roads

Understanding the safety and mobility impacts of Connected Vehicle (CV) applications is critical for ensuring effective implementations of these applications. This dissertation provides an assessment of the safety and mobility impacts of the Red-Light Violation Warning (RLVW), a CV-based application at signalized intersections, under pre-timed signal control and semi-actuated signal control utilizing Emulator-in-the-loop (EILS), Software-in-the-loop (SILS), and Hardware-in-the-loop simulation (HILS) environments. Modern actuated traffic signal controllers contain several features with which controllers can provide varying green intervals for actuated phases, skip phases, and terminate phases depending on the traffic demand fluctuation from cycle to cycle. With actuated traffic signal operations, there is uncertainty in the end-of-green information provided to the vehicles using CV messages. The RLVW application lacks accurate input information about when exactly a phase is going to be terminated since this termination occurs when a gap of a particular length is encountered at the detector. This study compares the results obtained with the use of these three aforementioned simulation platforms and how the use of the platforms impacts the assessed performance of the modeled CV application. In addition, the study investigates using HILS and a method to provide an Assured Green Period (AGP) which is a definitive time when the green interval will end to mitigate the uncertainties associated with the green termination and to improve the performance of the CV application. The study results showed that in the case of pre-timed signal control, there are small differences in the assessed performance when using the three simulated platforms. However, in the case of the actuated control, the utilization of EILS showed significantly different results compared to the utilization of the SILS and the HILS platforms. The use of the SILS and the HILS platforms produced similar results. The differences can be attributed to the variations in the time lag between vehicle detection and the use of this information between the EILS and the other two platforms. In addition, the results showed that the reduction in red-light running due to RLVW was significantly higher with pre-timed control compared to the reduction with semi-actuated control. The reason is the uncertainty in the end-of-green intervals provided in the messages communicated to the vehicles, as stated above. In the case of semi-actuated control, the results showed that the safety benefits of the RLVW without the use of AGP were limited. On the other hand, the study results showed that by introducing the AGP, the RLVW can reduce the number of red-light running events at signalized intersections by approximately 92% with RLVW utilization of 100%. However, the results show that the application of the AGP, as applied and assessed in this dissertation, can have increased stopped delay and approach delay under congested traffic conditions. This issue will need to be further investigated to determine the optimal setting of the AGP considering both mobility and safety impacts

Safety-critical scenarios and virtual testing procedures for automated cars at road intersections

This thesis addresses the problem of road intersection safety with regard to a mixed population of automated vehicles and non-automated road users. The work derives and evaluates safety-critical scenarios at road junctions, which can pose a particular safety problem involving automated cars. A simulation and evaluation framework for car-to-car accidents is presented and demonstrated, which allows examining the safety performance of automated driving systems within those scenarios. Given the recent advancements in automated driving functions, one of the main challenges is safe and efficient operation in complex traffic situations such as road junctions. There is a need for comprehensive testing, either in virtual testing environments or on real-world test tracks. Since it is unrealistic to cover all possible combinations of traffic situations and environment conditions, the challenge is to find the key driving situations to be evaluated at junctions. Against this background, a novel method to derive critical pre-crash scenarios from historical car accident data is presented. It employs k-medoids to cluster historical junction crash data into distinct partitions and then applies the association rules algorithm to each cluster to specify the driving scenarios in more detail. The dataset used consists of 1,056 junction crashes in the UK, which were exported from the in-depth On-the-Spot database. The study resulted in thirteen crash clusters for T-junctions, and six crash clusters for crossroads. Association rules revealed common crash characteristics, which were the basis for the scenario descriptions. As a follow-up to the scenario generation, the thesis further presents a novel, modular framework to transfer the derived collision scenarios to a sub-microscopic traffic simulation environment. The software CarMaker is used with MATLAB/Simulink to simulate realistic models of vehicles, sensors and road environments and is combined with an advanced Monte Carlo method to obtain a representative set of parameter combinations. The analysis of different safety performance indicators computed from the simulation outputs reveals collision and near-miss probabilities for selected scenarios. The usefulness and applicability of the simulation and evaluation framework is demonstrated for a selected junction scenario, where the safety performance of different in-vehicle collision avoidance systems is studied. The results show that the number of collisions and conflicts were reduced to a tenth when adding a crossing and turning assistant to a basic forward collision avoidance system. Due to its modular architecture, the presented framework can be adapted to the individual needs of future users and may be enhanced with customised simulation models. Ultimately, the thesis leads to more efficient workflows when virtually testing automated driving at intersections, as a complement to field operational tests on public roads

Future Transportation

Greenhouse gas (GHG) emissions associated with transportation activities account for approximately 20 percent of all carbon dioxide (co2) emissions globally, making the transportation sector a major contributor to the current global warming. This book focuses on the latest advances in technologies aiming at the sustainable future transportation of people and goods. A reduction in burning fossil fuel and technological transitions are the main approaches toward sustainable future transportation. Particular attention is given to automobile technological transitions, bike sharing systems, supply chain digitalization, and transport performance monitoring and optimization, among others

Developing urban transport in Turkey with much higher dependence on walking and cycling

A review of previous sustainable transportation scenarios has revealed that each key change usually did not represent an aspirational urban mode of transportation that was interconnected through underlying systemic relationships. Development of a framework that facilitates a set of quality criteria would, therefore, represent a significant advance in the evaluation and design of a sustainable vision. In that regard, this thesis presents a methodological framework, which inductively arrives at a systematic mechanism for developing sustainable transportation scenarios. It was determined that two essential steps needed to be taken to make this vision a reality. First, it was reasoned that convening with different users and professionals from various disciplines to investigate the reliability of this idea was the best approach. Second, the policies that need to be designed from the present to 2035 by the central and local administrations to achieve specific goals were discussed and evaluated by national and local decision makers. Overall, the conclusion of the thesis indicates that the content of our aspirational based proposal was credible and effective. Research approach provided an opportunity for several creative choices and alternatives to be determined by thoroughly addressing our research objectives. Future areas of research were also identified and described