1,720,998 research outputs found
Compensation effect between deaths from Covid-19 and crashes: The Italian case
Full text linkEmergencies such as the Covid-19 pandemic pose several decision-making issues, while clear evidence of successful strategies are still unavailable, different policies may be identified. However, in such emergencies, the preservation of public health, by firstly reducing human loss of life may be prioritized and then restrictive measures are implemented. The trade-off between damage due to the threat and the decrease in damage due to the lockdown is largely unexplored. Here we show that there is a degree of compensation between damage from epidemic deaths and from traffic deaths, especially in the case of immediate restrictive measures imposed by governments. Based on the Italian case, we found that damage from loss of human Capital and health care costs could have been fully compensated if the lockdown had been imposed ten days earlier. Considering only one Italian region (Puglia), where the epidemic was delayed and then restrictions were timely, damage due to loss of human Capital was largely compensated in the real scenario. However, damage due to loss of welfare could not have been fully compensated for, since Covid-19 deaths largely outnumber traffic deaths in the simulated epidemic period and loss of welfare damage is scarcely dependent on the age-at-death. From a broader perspective, societies seem to react to external threats as a whole organism, thus tending to restore the original equilibrium. Governmental decisions could accelerate this process. However, in the case of similar threats, some wounds cannot be compensated for, such as the incalculable damage due to loss of welfare
Connecting Rural Road Design to Automated Vehicles: The Concept of Safe Speed to Overcome Human Errors
No full textThe human-road-vehicle automated system is a challenge to overcome human errors. Several rural road crashes happen due to loss of friction, unlikely predictable by drivers. The friction diagram method (FDM) by the authors, described in previous papers, is able to evaluate the skidding risk taking into account vehicle, environmental, road factors. An important variable is the vehicle speed. According to the FDM, the speed corresponding to the maximum friction used can be computed. If all vehicles will travel at speeds lower than that, all other safety checks being verified, then the skidding risk can be reduced. Automated vehicles could travel at the safe speed predicted for each section, by acquiring all the necessary information directly from the road. The algorithm can be customized according to the particular vehicle, tires and road conditions. Additional remarks about the shift from traditional road design practice to the driving automation are also given
The deviation angle for one-lane roundabouts: A general mathematical formulation and application
No full textProperly designed roundabouts may lead to safety improvements based on both reducing approaching speeds and controlling traffic. Measurements of deflection of vehicle trajectories are commonly used to estimate roundabout speed control. One of these measurements is the deviation angle, which is mentioned in both the Italian and Swiss road standards and, in specific conditions, can be more effective than other methods. This article presents a general mathematical formulation for linking several geometric parameters with the deviation angle in different rural and urban one-lane roundabout configurations, which is currently missing in the literature. For urban roundabouts, refuge islands for pedestrians and cyclists were considered. Based on the proposed formulation, a sensitivity analysis of the influential geometric parameters was conducted. Results suggest that an insufficient deflection of trajectories (deviation angle less than 45°) is always present for roundabouts with inscribed circle diameter less than 25 m; for urban roundabouts with refuge islands for pedestrians and cyclists having inscribed circle diameter less than 34 m and orthogonal legs; and for roundabouts with angles between opposite legs smaller than 140°. The main parameters which are responsible for a decrease in the deviation angle are: a decrease in the inscribed circle diameter; a decrease in the angle between opposite legs; and an increase in the width of the circulatory lane. Some optimized procedures for roundabout design, the generalized application of the deviation angle method and alternative speed control measures in cases of small deviation angles are discussed
Route familiarity in road safety: A literature review and an identification proposal
No full textRoute familiarity can be an important safety-related variable, which is often neglected. A review of previous works highlighting the relationships between route familiarity and road safety in behavioural studies and engineering standards/frameworks has been conducted. Theoretical frameworks supported by experimental results have revealed that driving behaviour can be affected by route familiarity. The latter may lead to distraction and self-confidence; and in turn to more dangerous behaviours after repeated journeys. From an economic perspective, the possible worsening of driving safety performance may be explained by trade-offs with mobility benefits. Route familiarity is also considered in engineering practice. Road design guidelines assuming a “design driver” were suggested as implicitly preserving the safety of familiar/unfamiliar drivers. The mix of familiar and unfamiliar drivers in traffic flow is explicitly considered when computing the design traffic. The safety implications of these matters find only partial confirmation in previous studies focused on involvement in crashes. However, comparing those findings was difficult due to the high variability in measuring the route familiarity itself. An attempt to harmonize the possible identifications of familiarity for future studies, based on previous findings, is proposed. The proposal considers two different scales used for measuring route familiarity: one based on travelling frequency, the other on distance from residence
Integrated American-European protocol for safety interventions on existing two-lane rural roads
Full text linkThe main purpose was to integrate two strategies for road safety analyses (qualitative: audits, inspections; and quantitative: accident predictions) and develop a possible protocol for the safety interventions on existing two-lane rural road segments. Those road sections do not typically belong to the TEN-network, to which the 2008/96/EC Directive is mainly oriented. Hence, they could lack of methods for designing safety-based interventions. The main research questions were: Which possible problems can arise from the application of this protocol to real cases? Which data are practically needed? Which possible solutions can be provided for the highlighted problems? The integrated protocol, including: 1) the HSM predictive method, 2) the EU Regulations, 3) the local road design standards, 4) some research developments; is applied to real two-lane rural road segments requiring safety-based interventions. Its application is divided in the typical road safety analysis stages. A wide list of possible problems was highlighted and addressed: 1) lack of data, 2) difficult comparison with current road standards in order to identify safety problems, 3) lack of methods for evaluating the skidding risk along the layout, 4) setting speed limits, 5) need for optimizing the selection of countermeasures based on their aims and their timely application, in different recurrent situations, 6) availability and comparison of predictive methods. Based on the problems and solutions discussed, main advantages (1) the systematic approach, 2) the quantitative assessment of benefits, 3) the possible transferability) and disadvantages (difficulties in overcoming the lack of data and calibrated accident prediction models) of the method were remarked
The role of route familiarity in driving behaviour
No full textDifferences in driving behaviour due to the presence of users familiar (or
unfamiliar) with the road are considered in the Highway Capacity Manual (HCM)
procedure used to evaluate the level of service of Freeways and Highways. However,
although considered, the matter is largely unexplored: there is a lack of theoretical
foundations and data on determining the impact of route familiarity on accident
rates, speed choice and risk perception. On the other hand, some literature studies
confirm that route familiarity is influential on driving behavior, encouraging research
in this sense. In this paper, the authors propose some possible relationships between
route familiarity and road safety by considering an experiment carried out on a two
lane rural road and, in particular, by analysing how the habit of driving on a given
route could be influential in speed choice, risk perception and, potentially, on
accident rates too
Evaluating Skidding Risk of a Road Layout for All Types of Vehicles
No full textThis paper represents an updating of research previously begun by the authors concerning a new method to analyze the problem of friction of road vehicles. Starting from the 3rd criterion of Lamm, the new concept of “Friction Capital” was introduced in previous work, as the limit performance of the road in terms of friction. This method has been named Friction Diagram Method; its output is the Friction Diagram that represents the percentage of “Friction Capital” that a vehicle is using traveling on a given road. This percentage is defined as FUSED. During the design step, the Friction Diagram could be used in order to quantify the risk of skidding related to a given road layout. In this paper, the authors investigate the influence of the vehicle type on the Friction Diagram, since it was observed that the type of vehicle used in analyzing a road segment makes the values of FUSED change when the boundary conditions and the road geometry change. This aspect led the authors to identify the vehicle to be used in the skidding risk detection. This vehicle has been named as the “Design Critical Vehicle”(DCV). It allows faster detection of the road sections with high skidding risk using a single Friction Diagram and avoiding the need to perform the same analysis for various vehicle. The DCV identification could be useful in the application of the Friction Diagram Method both in road design and in checking of existing roads
Modelling the impact of wildfire smoke on driving speed
Full text linkTraffic models can be used to study evacuation scenarios during wildland-urban interface fires and identify the ability of a community to reach a safe place. In those scenarios, wildfire smoke can reduce visibility conditions on the road. This can have serious implications on the evacuation effectiveness since drivers would reduce their speed in relation to the optical density on the road. To date, there is no traffic model which explicitly represents the impact of reduced visibility conditions on traffic evacuation flow. This paper makes use of an experimental dataset collected in a virtual reality environment to calibrate two widely used macroscopic traffic models (the Lighthill-Whitham-Richards and the Van Aerde models) in order to account for the impact of reduced visibility conditions on driving speed. An application of the calibrated traffic model considering the impact of smoke has been performed using the WUI-NITY platform, an open multi-physics platform which includes wildfire spread, pedestrian response and traffic modelling. A dedicated verification test has been developed and performed considering different values of optical densities of smoke and traffic densities to ensure the model has been implemented correctly in WUI-NITY. A case study that demonstrates the applicability of the model to real life scenarios was also implemented, based on data from an evacuation drill. This paper shows that the presence of smoke on the road can significantly decrease movement speed and increase evacuation times thus highlighting the need for inclusion of this factor in traffic evacuation models applied for wildland-urban interface fire scenarios
Effects of Berlin speed cushions in urban restricted speed zones: a case study in Bari, Italy
Full text linkThe widespread European policy towards urban sustainable mobility requires some engineering-related interventions on the existing urban road network, such as traffic calming measures. There is a substantial amount of research assessing the effects of different traffic calming measures, even if there is no unanimous evidence for some of them, such as speed cushions (in particular Berlin speed cushions). Some research on speed cushions has been conducted, even if different results were achieved, also varying with the country and context of installation. Moreover, some of these studies are old and they need to be updated, given the continuous transformation of urban environments. In agreement with the City of Bari, thanks to ASSET-Puglia Region funds, the Italian Ministry of Infrastructures and Transport has granted permission to install speed cushions on three urban streets located in restricted speed zones (≤30 km/h) in the City of Bari, to test their effects on vehicular traffic. In this context, this article is aimed at assessing the preliminary results obtained, considering the effects on vehicular speeds. The study design is a typical before-and-after study, in which speeds are measured using a laser speed gun on the three selected road segments before and after the implementation of speed cushions (for each segment, the cushion has a different width). Visual observations were also useful to detect the effects of speed cushions on trajectories and speeds of two-wheeled vehicles. The preliminary analysis of speed profiles revealed a consistent decrease in speed for all the three test sites (in particular the operating speed V85, which is reduced by up to approximately 30%). Moreover, it seems that the decrease in speed is more evident as the cushion width decreases
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