In the United States, there were 36,560 traffic-related fatalities in 2018, of which 20% were pedestrians, bicyclists, and other vulnerable road users (VRUs) [1]. Vulnerable road users are non-vehicle occupants who, because they are not enclosed in a vehicle, are at higher risk of injury in traffic crashes. While overall traffic fatalities in the US have been decreasing, pedestrian and bicyclist fatalities have been trending upward. Vehicle-based active safety features could avoid or mitigate crashes with VRUs, but are highly dependent on the ability to detect a VRU with enough time or distance. This work presents methods to examine the characteristics of vehicle-pedestrian and vehicle-bicycle crashes and near-crashes using a variety of data sources, assess the potential effectiveness of Automatic Emergency Braking (AEB) in avoiding and mitigating VRU crashes through modeling and simulation, and estimate the future benefits of AEB for VRU safety in the United States. Additionally, active safety features are most effective when behavior of VRUs can be anticipated, however, the behavior of pedestrians and bicyclists is notoriously unpredictable. Therefore, an approach to examine and categorize pedestrian behavior in response to near-crashes and crashes events is presented. Overall, findings suggest that AEB has great potential to avoid and mitigate collisions with pedestrians and bicyclists, but it cannot avoid all crashes even when an idealized AEB system is assumed. Most pedestrians and bicyclists were found to be visible for at least one second prior to the crash, but obstructions, the unpredictability of VRUs, and adverse weather/lighting conditions still pose challenges in avoiding and mitigating crashes with VRUs. / Doctor of Philosophy / In the United States, there were 36,560 traffic-related fatalities in 2018, of which 20% were pedestrians, bicyclists, and other vulnerable road users (VRUs) [1]. Vulnerable road users are non-vehicle occupants who, because they are not enclosed in a vehicle, are at higher risk of injury in traffic crashes. While overall traffic fatalities in the US have been decreasing, pedestrian and bicyclist fatalities are trending upward. Vehicle-based countermeasures, such as Automatic Emergency Braking (AEB), could avoid or mitigate crashes with VRUs, but are highly dependent on the ability to detect a VRU with enough time or distance. My work presents methods to examine the characteristics of vehicle-pedestrian and vehicle-bicycle crashes and near-crashes using a variety of data sources, assess the potential effectiveness of AEB in avoiding and mitigating VRU crashes through modeling and simulation, and estimate the future benefits of AEB for VRU safety in the United States. Additionally, crash avoidance technologies are most effective when behavior of VRUs can be anticipated, however, the behavior of pedestrians and bicyclists is notoriously unpredictable. Therefore, I examined and categorized pedestrian behavior in response to near-crashes and crashes events. Overall, we found that AEB has great potential to avoid and mitigate collisions with pedestrians and bicyclists, but it cannot avoid all crashes even when assuming an idealized AEB system. Most pedestrians and bicyclists were found to be visible for at least one second prior to the crash, but obstructions, the unpredictability of VRUs, and adverse weather/lighting conditions still pose challenges in avoiding and mitigating crashes with VRUs.

Planläggning av cirkulationsplatser har blivit ett vanligt inslag i en mängd olika städer världen över för att lösa farliga situationer som kan uppstå i traditionella fyrvägskorsningar. Detta eftersom bilisternas hastighet hålls låg i en cirkulationsplats jämfört med en vanlig fyrvägskorsning vilket i sin tur leder till mindre allvarliga olyckor. Är de oskyddade trafikanternas säkerhetsfördelar vid en cirkulationsplats lika tydliga? Syftet med studien är att undersöka utformningen av trafikmiljöer, med fokus på fotgängares och cyklisters säkerhet i anslutning till cirkulationsplatser. Jag har sett på vilka säkerhetshöjande aspekter som bör tas i beaktande för oskyddade trafikanter. Frågeställningarna i arbetet är - Vilka för- och nackdelar för oskyddade trafikanter finns det med planläggning och konstruktion av cirkulationsplatser? - Vilka säkerhetsaspekter tas i beaktande vid cirkulationsplatser? Forskningen baserar sig på en kvalitativ metod. Datainsamlingsmetoder som använts är observation, intervju och kvalitativ textanalys. I undersökningen deltog tre planerare från Gävle, Eskilstuna och Västerås. I undersökningen lyfts säkerhetsaspekter, samt för- och nackdelar fram som de undersökta kommunerna utgår ifrån i planläggningen av cirkulationsplatser och övergångsställen. I resultatet kan konstateras att det med snabba och relativt enkla metoder och åtgärder är möjligt att förbättra fotgängares och cyklisters säkerhet på passager vid cirkulationsplatser. / Planning of roundabouts have become a common feature in various cities around the world to resolve dangerous situations that may occur in traditional four-way intersections. This is because the motorists’ speed is lower in a roundabout compared to a standard four-way intersection, which leads to less severe accidents. Are vulnerable road users safety benefits at a roundabout as clear? The purpose of the study is to examine the design of traffic environments, with a focus on pedestrian and cyclists’ safety in connection to roundabouts. I have seen on the safety aspects that should be taken into consideration for pedestrians and cyclists. The research questions in my study are: - What are the advantages and disadvantages of vulnerable road users with planning and construction of roundabouts? - Which safety aspects are taken into consideration in roundabouts? The research is based on a qualitative approach. Data collection methods used are observation, interview and qualitative text analysis. The study included three planners from Gävle, Eskilstuna and Västerås. The highlighted safety aspects, advantages and disadvantages presented by the surveyed municipalities proceed from with planning of roundabouts and pedestrian crossings. In the result it can be stated that with fast and relatively simple methods and steps are possible to improve pedestrian and cyclist safety on crossings at roundabouts.

Traffic-related injuries represent a global public health problem, and contribute largely to mortality and years lived with disability worldwide. Over the course of the last decades, improvements to road traffic safety and injury surveillance systems have resulted in a shift in focus from the prevention of motor vehicle accidents to the control of injury events involving vulnerable road users (VRUs), such as cyclists and moped riders. There have been calls for improvements to the evaluation of safety interventions due to methodological problems associated with the most commonly used study designs. The purpose of this licentiate thesis was to assess the strengths and limitations of the interrupted time series (ITS) design, which has gained some attention for its ability to provide valid effect estimates. Two national road safety interventions involving VRUs were selected as cases: the Swedish bicycle helmet law for children under the age 15, and the tightening of licensing rules for Class 1 mopeds. The empirical results suggest that both interventions were effective in improving the safety of VRUs. Unless other concurrent events affect the treatment population at the exact time of intervention, the effect estimates should be internally valid. One of the main limitations of the study design is the inability to identify why the interventions were successful, especially if they are complex and multifaceted. A lack of reliable exposure data can also pose a further threat to studies of interventions involving VRUs if the intervention can affect the exposure itself. It may also be difficult to generalize the exact effect estimates to other regions and populations. Future studies should consider the use of the ITS design to enhance the internal validity of before-after measurements. / Traffic-related injuries represent a global public health problem, and contribute largely to mortality and years lived with disability. Over the course of the last decades, improvements to road traffic safety and injury surveillance systems have resulted in a shift in focus from motor vehicle accidents to injury events involving vulnerable road users (VRUs), such as cyclists and moped riders. There have been calls for improvements to the evaluation of safety interventions due to methodological problems associated with the most commonly used study designs. The purpose of this licentiate thesis was to assess the strengths and limitations of the interrupted time series (ITS) design, which has gained some attention for its ability to provide valid effect estimates while accounting for secular trends. Two national interventions involving VRUs were selected as cases: the Swedish bicycle helmet law for children under the age 15, and the tightening of licensing rules for Class 1 mopeds. The empirical results suggest that both interventions were effective. These results are discussed in the light of some methodological considerations regarding internal and external validity, data quality and the ability to fully understand key causal mechanisms behind complex interventions.

Introduction : La sécurité routière sur le réseau interurbain est un problème majeur de santé publique dans les Pays à Revenu Bas et Moyen (PRBM) mais peu d'attention y a été consacrée. Les objectifs de cette thèse étaient d’évaluer le fardeau des traumatismes en relation avec le trafic interurbain, la déclaration des usagers blessés dans des bases de données différentes, d’analyser l’association entre les facteurs situationnels (caractéristiques physiques et circonstances environnementales) et les sites des accidents et la perception de la dangerosité des tronçons accidentogènes dans les PRBM. Méthodes et résultats : Pour répondre à ces objectifs, cinq études spécifiques ont été réalisées dans deux PRBM, le Cameroun et le Pakistan. L’étude I a évalué le nombre de tués par véhicules-km parcourus et les facteurs qui leur étaient associés, en utilisant les rapports de police entre 2004 et 2007 sur l’axe Yaoundé-Douala, Cameroun. Le taux de mortalité était de 73 par 100 millions véhicules km parcourus, un taux 35 fois plus élevé que sur un même type de route en pays à revenu élevé. La mortalité était plus élevée pour les accidents impliquant des usagers vulnérables, les véhicules roulant en sens opposé et ceux dus à une défaillance mécanique, y compris un éclatement de pneu. L’étude II a évalué les différences de déclaration d’accidents faites par les services de police, d’ambulance et des urgences en 2008 sur l’axe Karachi-Hala, Pakistan. La mortalité était de 53 par 109 véhicules-km parcourus ; le taux de mortalité était 13 fois plus élevé sur cet axe par rapport à un même type de route en France. La police a déclaré un mort sur cinq et un blessé grave sur dix. Les usagers de la route vulnérables, y compris les piétons et deux-roues ont été deux fois moins déclarés par la police que par les services d'ambulance ou des urgences. L’étude III a étudié les facteurs situationnels associés aux sites des accidents sur l’axe Yaoundé-Douala par une approche de type cas-témoins. Les facteurs tels que le profil routier plat (rapport de cotes [RC] ajusté =1,52 ; intervalle de confiance à 95 % [IC95 %]=1,15-2,04), les surfaces irrégulières (RC=1,43 ; IC95 %=1,04-1,99), les obstacles à proximité (RC=1,99 ; IC95 %=1,09-3,63) et les intersections à trois (RC=3,11 ; IC95 %=1,15-8,39) ou à quatre directions (RC=3,23 ; IC95 %=1,51-6,92) étaient significativement associés à des sites d’accidents corporels. De plus, la probabilité des accidents augmentait dans des zones urbaines situées dans des régions de plaine (RC=2,23 ; IC95 %=1,97-2,77). L’étude IV a étudié le fardeau des traumatismes dus aux accidents ainsi que les facteurs associés dans des zones en travaux sur l’axe Karachi-Hala en utilisant les méthodes de cohorte historique. Un tiers de la mortalité routière était survenu dans des zones en travaux et le risque de mortalité était quatre fois plus élevé dans ces zones que dans les autres zones. Un accident sur deux a eu lieu entre des véhicules roulant en sens opposé dans ces zones. L’étude V a étudié la perception de la dangerosité des tronçons accidentogènes (au moins 3 accidents sur 3 ans) et non accidentogènes (aucun accident déclaré) sur les deux axes des précédentes études, en montrant leurs vidéos à des conducteurs volontaires pakistanais. Les conducteurs n’ont perçu comme dangereux que la moitié des tronçons accidentogènes. La perception de la dangerosité des tronçons plats et droits était plus faible par rapport aux tronçons en courbes et avec une pente. La perception de la dangerosité en zone urbaine d’un tronçon accidentogène était significativement moins élevée (RC=0,58 ; IC95 %=0,51-0,68) que celle d’un tronçon non accidentogène ayant la même caractéristique (RC=2,04 ; IC95 %=1,51-2,74). La perception de la dangerosité d’un tronçon accidentogène avec panneau de signalisation était significativement plus élevée (RC=2,75 ; IC95 %=2,38-3,16) par rapport à des tronçons non accidentogènes ayant la même caractéristique (RC=0,50 ; IC95 %=0,34-0,72). Conclusion : Cette thèse montre combien des méthodes épidémiologiques simples, mais novatrices, peuvent être utiles pour évaluer le fardeau des traumatismes par accidents et leurs facteurs de risques dans les PRBM. Ces pays sont confrontés à un énorme fardeau de morbidité routière qui est souvent sous-déclarée dans les données de la police. Un système de surveillance fiable et valide est nécessaire dans les PRBM. De plus, la politique de prévention pourrait être améliorée par une meilleure communication d’information entre les autorités routières et policières concernant les facteurs situationnels. De la même façon, les mesures de sécurité dans les zones en travaux devraient être contrôlées par un système dédié. Enfin, la sécurité routière sur les routes interurbaines dans les PRBM pourrait être améliorée en rendant les routes plus « informant », en particulier avec l’application de mesures peu couteuses telles que les panneaux de signalisations sur les tronçons accidentogènes. / Background: Interurban traffic safety is a major public health problem, but has received little attention in Low- and Middle-Income Countries (LMICs). The objectives of this thesis were to assess the burden of injury related to interurban traffic, and reporting of these injuries in different datasets, to analyze situational factors (physical characteristics and environmental circumstances) associated with crash sites, and road hazard perception of high-risk crash sites in LMICs. Methods and results: These objectives were assessed in five specific studies conducted in two LMICs, Cameroon and Pakistan. In study I, traffic fatality per vehicle-km and associated crash factors were assessed using police reports for years 2004 to 2007, on the two-lane Yaoundé-Douala road section in Cameroon. Traffic fatality was 73 per 100 million vehicle-km, a rate 35 times higher than a similar road in a high-income country. Fatality was higher for crashes involving vulnerable road users, crashes between oppositely-moving vehicles, and those due to mechanical failure including tyre burst. In study II, traffic injury reporting to police, ambulance, and Emergency Department (ED) in 2008 was assessed, on the four-lane Karachi-Hala road section in Pakistan. Crash fatality was over 53 per 109 vehicle-km, a rate 13 times higher than a similar road in France. Police reported only one out of five fatalities and one out of ten severe injuries. Vulnerable road users were two times less reported in police data than ambulance or ED data. In study III, situational factors associated with injury crash sites were assessed on the Yaoundé-Douala road section, using case-control methods. Factors such as flat road profiles (adjusted Odds Ratios [OR]=1.52; 95% Confidence Interval [95%CI]=1.15-2.01), irregular surface conditions (OR=1.43; 95%CI=1.04-1.99), nearby road obstacles (OR=1.99; 95%CI=1.09-3.63), and three- (OR=3.11; 95%CI=1.15-8.39) or four-legged (OR=3.23; 95%CI= 1.51-6.92) intersections were significantly associated with injury crash sites. Furthermore, the likelihood of crash increased with built-up areas situated in plain regions (OR=2.33; 95%CI=1.97-2.77). In study IV, traffic injury burden and factors associated with Highway Work Zones (HWZs) crashes were assessed on the Karachi-Hala road section, using historical cohort methods. HWZs accounted for one third of traffic fatalities, and fatality per vehicle-km was four times higher in HWZs than other zones. One out of two HWZ crashes occurred between oppositely moving vehicles. In study V, hazard perception of high-risk (with ≥ 3 crashes in 3 years) and low-risk sites (no crash reported) from the two above road sections was assessed by showing videos to voluntary Pakistani drivers. Drivers were able to identify only half of the high-risk sites as hazardous. Sites with a flat and straight road profile had a lower hazard perception compared to those with curved and slope road profile. High-risk sites situated in built-up areas were perceived less hazardous (OR = 0.58; 95%CI=0.51-0.68) compared to low-risk sites (OR = 2.04; 95%CI=1.51-2.74) with same road situation. Further, high-risk sites with vertical road signs were more likely to be perceived hazardous (OR = 2.75; 95%CI=2.38-3.16) than low-risk sites (OR = 0.50; 95%CI=0.34-0.72) with such signs. Conclusion: This thesis illustrates how innovative yet simple epidemiological methods can be useful in assessing the injury burden and specific risk factors in LMICs. These countries face a high burden of interurban road injuries, mostly under-reported in police data. A reliable and accurate injury surveillance system is needed in these countries. Moreover, prevention policy can be improved by better information transfer between road and police authorities regarding situational factors. Similarly, a monitoring system is required to examine the HWZ safety interventions in these countries. Lastly, interurban road safety can be improved by making roads self-explaining, especially by implementing low-cost interventions such as vertical signs at high-risk sites.

Cycling as a mode of transportation has been recording an upward trend in both the U.S. and Europe. Unfortunately, the safety of cyclists has been a point of growing concern. Data from the National Highway Traffic Safety Administration (NHTSA) show that the crashes that occur during the events of motorists overtaking cyclists was one of the leading categories involving cyclists in fatal crashes. In support of the efforts to understand the driving behavior of drivers of motorized vehicles while overtaking cyclists, this research project is aimed at developing an algorithm to identify the overtaking events. Most existing quantitative studies on cycling safety leverage instrumented bicycles or vehicles with sensors for extracting naturalistic driving trajectories. Whereas we use data from a recent research that provides naturalistic driving trajectories of road users collected at select intersections in urban areas in Germany using drones equipped with cameras. Using these videos with a data frequency of 25 Hz, the authors of this study have output inD dataset. The inD dataset contains trajectories of road users that are captured in form of coordinates on a two-dimensional plane obtained from the ariel or bird's eye view of the road. Additionally, the data also captures velocity, acceleration, heading angles, dimensions of driver's vehicle etc. Overtaking can be thought of as four phases of approaching, steering away, passing, and returning. Using the inD dataset, we have developed an algorithm to identify events when a driver of motor vehicle overtakes a cyclist. This work fits into our broader goal to contribute to the body of knowledge for improving road safety of cyclists. The work is expected to provide inputs to governmental/ traffic authorities in aspects such as design of intersections and design of bicycle lanes by providing insights into overtaking events. [from Indroduction]

Mobility has changed in recent years in cities worldwide, th.anks to tb.e strong rise in vehicles of micromobility. Bicycle riding is the most widespread micromobility transport mode, followed by stand-up electric scooters (e-scooters). This increase in its use has also led to an increase in related crashes. Both cyclists and e-scooter riders are vulnerable road users and are lik.ely to sustain severe injuries in crashes, especially with motor vehicles. The crashes consequences involving cyclists and other micromobility users have already investigated using numerical simulation software, such as MADYMO and PC-Crash. Most of them have been focused on bicycles and electric bicycles, whereas only few of tbem have analyzed e-scooter crashes consequences. Posirisuk: et al. [1] carried out a computational prediction ofhead-ground impact k:inematics :in e-scooter falls. Ptak et al. [2] analyzed the e-scooter user kinematics after a crash against SUV when the e-scooter chives into the sidefront of tbe vehicle, a side B-pillar crash and a frontal impact initiated by tbe e-scooter to tbe front-end of the vehicle. However, they did not study the consequ.ences of a car to e-scooter side impact crashes. Xu et al. [3] did study these crashes but considering electric self-balancing scooters that are less widespread than e-scooters. Current study focuses on the consequences of a car to micromobility user (cyclist and e-scooter rider) side impact crashes. The analysis is based on numerical simulations with PC-Crash software.

IAB one solution of micromobility, e-scooters have become a trend in Germany. However, the concems about the safety of e-scooter riders, influence on pedestrians and the parking issues are growing. In 2020, 2,155 e-scooters involved personal injury accidents were recorded in Germany. The number rose to 5,502 in 2021 meaning an increase of 155.31 %. Compared to cyclists (incl. pedelec cyclists), the increasing rate of personal injury accidents in the same period decreased by 8.75 % [1, 2]. Against the background of accidents with e-scooters in cities, prior studies analysed severity and patterns of injuries caused by such accidents [3, 4]. In addition, comparisons are drawn to the consequences of accidents with other vehicles [5, 6]. Some studies also consider the risk of injuries in relation to the miles travelled [7]. The studies provide valuable findings but the approaches focus on the severe consequences of occurred accidents. At the same time, compared to bicycles, the centre of gravity of e-scooters is lower, they are more manoeuvrable and can still reach speeds of up to 20 km/h [8]. The question remains, if these vehicle characteristics are associated with different interaction behaviour. Hence, the aim of the present study is to reveal the riding behaviour profile in different contexts and investigate e-scooter riders' criticality in interaction behaviour compared with cyclists using surrogate safety measures. We aim to figure out if the interaction behaviour of the two modes differ and what the effects of potential differences are for safety considerations in the system of active mobility.

Cycling as an active mode of transport is increasing across all Europe [1]. Multiple benefits are coming from cycling both for the single user and the society as a whole. With increasing cycling, we expect more conflicts to happen between cyclists and vehicles, as it is also shown by the increasing cyclists' share of fatalities, contrary to the passenger cars' share [2]. Understanding cyclists' behavioral patterns can help automated vehicles (AVs) to predict cyclist's behavior, and then behave safely and comfortably when they encounter them. As a result, developing reliable predictive models of cyclist behavior will help AVs to interact safely with cyclists.

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In recent years, accidents between trucks and other vehicles have decreased while accidents be-tween trucks and vulnerable road-users have increased. The reason for this is unknown, which is why this Master’s Thesis project was initiated. The project is a co-operation between two students from two different universities, LTU and KTH, done for Volvo GTT in Gothenburg. A user study containing interviews and co-rides has been executed with truck drivers in the Gothenburg area during the autumn of 2017. A survey was also sent to different organizations for cyclists, motorcyclists, car drivers and to Facebook groups for the two universities. Critical situations mentioned by the truck drivers were chosen with the help of the survey answers from other road-users. Right hand turns with a truck that crosses a bike lane and intersections with a zebra crossing were the situations the project focused on, based on the Volvo Trucks Safety Report 2017 which stated those situations as the most dangerous. Serious accidents occurring when a truck turns right is when vulnerable road-users end up under the truck’s back wheels, which cuts corners. This made the project focus on trying to find a solution that could reduce this type of accident. The project also concentrated on increasing the commu-nication at intersections, based on the survey comments where it became clear that eye contact is insufficient, which led to focus on communication between trucks and fellow road-user instead. Through benchmarking, literature reviews and idea generation the final concept solution was cre-ated and developed after a workshop. The final concept solution is a turning projection that visualizes the dangerous area when a truck is turning and a light matrix in the front grille for increasing the understanding, visually, of the truck driver’s intentions of slowing down or speeding up. The final concept solution contains a zebra crossing projection in the front of the truck to facilitate the communication today, and in the future to even replace eye contact and gestures done between truck driver and fellow road-users at crossings. Further development of the concept solution includes choices and adaption of available technology and research concerning legislation for color usage on lights and projections to the front and sides of the trucks.