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Multi-fidelity algorithms for solving the horizontal alignment problem in road design are considered. A multi-fidelity surrogate model is built and quantile regression is used to understand its accuracy at various fidelity levels. Two algorithms are compared: a generalized pattern search algorithm with adaptive precision control, and a trust-region algorithm for unconstrained problems with controlled error. To make a fair comparison, the parameters of each algorithm are tuned on five small roads using performance profiles. Then the algorithms are evaluated on 35 roads, ranging from small to very large roads. The results show that using multi-fidelity surrogates in optimization algorithms provide notable speed-up when compared to single-fidelity algorithms while preserving the quality of solutions (cost error < 1 %). On the longest roads, higher speed-up and better accuracy are observed. [ABSTRACT FROM AUTHOR]

Objectives: Mixed-use urban environments, such as arterial roads with adjacent commercial land uses, represent crash locations with the highest risk. These locations are often characterized by high volumes of motor vehicle traffic, on-street parking, and interactions with multiple road user groups such as pedestrians, cyclists, and public transportation. The objective of this study was to investigate previously identified crash risk factors for mixed-use urban environments and assess how parking occupancy, center medians, and cyclist volume influence performance and workload in a driving simulator study. Methods: Thirty participants were recruited for the study. Participants completed 6 drives that presented different combinations of cyclist volume, median condition, and parking occupancy. Incorporated into the simulator drives was a secondary peripheral detection task (PDT) designed to measure mental workload. Participants provided subjective assessments of workload using the Rating Scale Mental Effort (RSME). Results: Mean lateral lane position was found to significantly vary across the 3 independent variables of parking occupancy, cyclist volume, and median conditions. No significant changes were identified for mean speed across the conditions. Subjective and objective measures of workload identified changes due to the presence of cyclists with slower reaction times for the PDT task when cyclists were present. Conclusion: The findings provide insight into the interaction of road design elements in mixed-use urban road environments and demonstrate that increasingly complex environments increase driver demand. This has important road design implications for mixed-use arterial roads, which are often characterized by complex interactions between multiple road user groups. [ABSTRACT FROM AUTHOR]

In the last decade, many single carriageway roads in Sweden have been converted to collision-free roads as a cost-effective alternative to conventional motorways. Investigations have concluded that the road type has been successful in reducing the number of fatal accidents, despite increased operation and maintenance costs. In recent years, the focus has shifted to converting narrower roads which are anticipated to further increase operation and maintenance cost but also complicate traffic management during road works. There are concerns that when life cycle cost is considered in the investment assessment the socioeconomic profitability could be reduced. This article examines this issue by first assessing changes in costs for operation and maintenance using a life cycle cost analysis approach applied on a case study. The results from the analysis were thereafter integrated into a cost–benefit analysis to assess changes in costs in relation to benefits in improved traffic safety and travel time. The analysis indicated profitability even with substantial increase in operation, maintenance and road user work zone costs. Results are discussed from project implementation and road management perspectives. [ABSTRACT FROM AUTHOR]

Several studies have indicated that road crashes are more likely to occur on horizontal curves than on straight roadway segments for a good number of reasons, the most important of which is associated with the driver's behavior along the curve depending on his or her perception of the road geometry. However, the evaluation of the effects of curve features on driving performance still remains a critical issue for road safety and design. The main objective of this study is to investigate driver's behavior and his perception of road curves, which is directly related to road safety. Specifically, the effects of some curve features (radius, transition curve, visibility, cross-section) on driving performance are investigated through a multifactorial experiment based on driving simulation. The driving speeds and trajectories of a sample of 34 drivers were statistically processed over 72 different curves distributed along three test scenarios. The main and interaction effects of the independent variables are described and discussed in the Results section providing a significant improvement of the actual knowledge in this field of research. In general, the results confirm that driving simulation can disclose the relationships between road design features and driver behavioral aspects that are crucial issues in creating a safer road infrastructure. [ABSTRACT FROM AUTHOR]

The proposed research addresses the problem of predicting driver's visual behavior. Notably, this issue is of great importance for road safety because it provides information about the true perception of the road environment. This need is particularly felt when the real situation is so complex that it cannot be represented by simple analytical audits contained in the road international standard. Therefore, with the help of an instrumented vehicle, the authors conducted some trials to identify relevant data useful to recognize the road environment as perceived by drivers. Based on this data, the authors prepared a linear model that, properly calibrated, would enable them to predict the drivers’ visual strategy. The results were encouraging, because a model so simple in structure as well as in the number of variables involved could control a very complex phenomenon, such as that of visual perception. The proposed methodology can be applied as a further control in the design of new roads and in the maintenance of existing ones and, in particular, in the analysis of special scenarios (e.g., unusual conditions of weather or traffic) that are not represented by ordinary audits contained in the road standards. [ABSTRACT FROM PUBLISHER]

Crashes in Sweden taken from Folksam in-depth studies were used to show how crash severity depends on various road environments. Crash severity was shown for various speed limits, crash types and road surface friction. Data used were from 422 frontal vehicle crashes in Sweden with recorded crash pulses. The findings of the current study showed that the average change of velocity was 4.6 ± 4.1 km/h higher on roads with a 90 km/h speed limit than on roads with a 70 km/h speed limit. The corresponding difference between 90 km/h and 50 km/h speed limit was 7 ± 5.9 km/h. In single vehicle crashes into guardrails, average change of velocity was 6.6 ± 4.1 km/h lower than into ditches, stones and rocks. The corresponding difference for average mean acceleration was 1.2 ± 0.8g. Two vehicle crashes on rural and urban roads with oncoming vehicles, which had an average change of velocity of 31.8 km/h and an average mean acceleration of 8.6g, constituted the crash type with the highest crash severity. There was a significant increase in crash severity for single vehicle crashes with respect to increasing surface friction. This study shows that the average impact severity of crashes depends not only on the struck object itself, but also on the traffic environment in which the crash occurs. In the development of new safety technologies, real-world crash severity data are valuable as input in attempts to predict the safety effect of these systems in various road traffic designs. [ABSTRACT FROM AUTHOR]

One of the key components of inflatable restraint systems is the gas generator (inflator). This relevance of the generator is mainly due to the fact that it is the only active component on most airbag systems. Each new car model requires a new process of developement and system integration to set up the performance of the restraint system. This process usually demands a performance adjustment of the gas generator to optimise the overall behaviour of the whole system. Often, the number of gas generator configurations available from serial or prototype manufacturing does not cover the whole range of each design parameter. Also, the time needed to manufacture a prototype definition of a gas generator can be delayed from some days to several months, depending on the extent of the required modifications. This process can be significantly shortened by a simulation approach that provides the performance at the output of a particular gas generator. The present work describes a new analytical model of a pyrotechnical gas generator developed in Matlab/Simulink code. The advantage of the selection of this software is that it can be linked with most of the vehicle crash simulation softwares currently available in the market. Also, the utilisation of the block modelling technique of Simulink allows the easy implementation of new capabilities to the model. The model has been built to reproduce the performance of the inflator measured on the widely accepted closed tank test. Finally, to guarantee the predictability of the model it has been validated by means of (1) the comparision, made at three different test temperatures, of the theoretical results with the baseline of the results of the tank pressure tests performed during one year of serial production of a particular gas generator model; (2) comparing gas generator variability limits for tank test performance, calculated with the same serial production gas generators, with the variability limits obtained by means of a Monte Carlo analysis using the analytical model. It is demonstrated by means of this validation of robustness of the presented model. [ABSTRACT FROM AUTHOR]

According to national (Greek) and European legislation on road infrastructure safety management, road safety auditing is mandatory for the Trans-European Road Network. This paper presents the development of a training course and educational material for candidate road safety auditors in Greece, aiming to adequately prepare them to conduct road safety audits. In particular, the principles upon which the road safety audit training course is based, the learning objectives, the course outline and the proposed framework of the curriculum are presented. The training course takes into consideration recent developments in road safety, as well as local conditions and needs. Because it places emphasis on the implementation of the Safe System and human factors in road design, it may contribute to the development of a positive safety culture among highway professionals involved in the road design and road operation process. The process of its development may be regarded as a proposal for good practice for the development of professional development training programmes, addressing the relevant training needs and achieving the relevant training objectives. [ABSTRACT FROM AUTHOR]