Session 19 – Road Safety Management

Matjaz Sraml, Tiziana Campisi, Giovanni Tesoriere, Antonino Canale and Chiara Gruden- The evaluation of the surrogate safety measures along a pedestrian confined ramps of an old bridge / Pedestrians walk daily to meet their basic needs. Therefore, over the years it has been attempted to make urban context more liveable, respecting the needs of weak road users which are a tourists and locals. Pedestrian mobility is also growing strongly from the point of view of tourism, especially in the areas where government measures are taken to reduce vehicular flow in order to let the architectural and landscape assets more usable.

Often tourist itineraries are made of narrow areas crossed by numerous pedestrians, leading to possible critical circumstances. The criticality is connected to a likely reduction of safety and use (comfort and possible delays). Confined spaces such as small streets or pedestrian bridges well exemplify the described situation. Particularly, pedestrian bridges are often composed of ramps with variable slopes and consist of different floors, making walking difficult and therefore reducing travel speed and limiting the mobility of users such as handicapped or elderly people.

Starting from the geometrical evaluation of the old bridge of Mostar (BIH), this article provides some ideas for evaluating the safety of pedestrians during the journey on the bridge, under different flow conditions.
The analyses were carried out starting from an estimate of pedestrian flows from video monitoring. Safety was then assessed thanks to the calculation of surrogate measures, based on the trajectories of individuals, obtained through tracking tools.

Camera monitoring and inspections to survey infrastructure’s geometric features ease the procedure of data entering into image processing software.

The evaluation of individual pedestrian trajectories and/or their interactions allows estimating the movement variations through the study of parameters such as speed variation, pedestrian density and surrogate safety factors.
Surrogate safety measures, indeed, are indicators calculated for a chosen pair of users interacting in the detected scene. Among these factors, there are: relative speed (Delta-V), Time-To-Collision (TTC), Time Advantage (TAdv) and T2. All the above-mentioned kinds of measures are interesting to study generally the behavioural aspects of road traffic and, specifically, safety level and factors influencing it.
The purpose of this work is to estimate the effects of induced pedestrian mobility on Mostar’s Ottoman bridge in terms of safety, with the aim of preventing negative scenarios that could lead to a bad infrastructural level of service. Conclusions are : importance of video-footages to achieve pedestrian flow data in confined spaces and pro-active check of safety and consequent mitigation of collision risk and for the end critical ramp zones have been identified an opportunity of improvement. The presenter pointed that one of possible solution could be installation of handrail to divide two path areas and also useful for older people.

Kateřina Bucsuházy, Robert Zůvala, Eva Matuchová, Martina Kostíková, Pavlína Dvořáková and Roman Mikulec- The Comprehensive Analysis of Traffic Accidents Causation / Analysis of accident causation does not allow to clearly determine the influence of one specific cause. Traffic accident has been a result of many interacting factors. Most of accident causes classification systems have been focused on the errors and actions of the participant that immediately led to the conflict (eg. not giving a way). The actual reasons why the driver failure occurred are not taken into account.
The aim of this study has been the analysis of all factors related to accidents and influenced the accident causation. For the purpose of this study, the most often factors contributing to the traffic accidents occurrence of selected risk groups has been analyzed – eg. young drivers, seniors, motorcyclists, man, woman, road familiarity,
For the data analysis, data from the research project Czech In-depth Accident Study (CzIDAS) has been used, started from 2011 with 1900 cases, it’s about 200 cases for a year. Mapping of the cases and time in collaboration with Ministere of Transport of Chech Republic were about 12 hours shift and they did not used a drone because of legal reasons of Chech Republic.The in-depth accident investigation teams document all relevant information on the traffic environment, vehicles, and human factors, at the scene immediately after the occurrence of a traffic accident. The investigation includes an individual interview by a psychologist with traffic accident participants, focused on all relevant information related to causes, actual mental and physical condition of a participant, driving habits and practice, and basic and sociodemographic and general information about the participant.

Vittorio Astarita and Vincenzo Pasquale Giofrè- Microsimulation and the evaluation of safety levels in the presence of roadside obstacles / Recent research papers have been devoted to the potential of traffic microsimulation for the analysis of road safety. In particular, some studies have confirmed that the reproduction by simulation of user behavior under different traffic flows and geometry conditions can identify near crashes events that are a good base to estimate real crashes risk. According to recent researches it appears that microsimulation tools can evaluate road safety performance and allow engineers to take appropriate countermeasures at specific points of the road network.
The results of these approaches have been promising, though, all ongoing research has overlooked one important issue in the estimation of traffic safety levels: single vehicle crashes.
According to statistics, collisions with fixed objects result in way above 40% of all vehicle fatal crashes. Common used safety indicators are limited in their application since, in fact, they are based on conflicts techniques that do not consider roadside obstacles and barriers.
The objective of this paper is to present a new approach to conflict techniques, for the evaluation of safety, which considers also potential conflicts with roadside objects. A specific microsimulation model add-on has been developed for the estimation of new road safety indicators that considers also potential crashes with roadside objects in addition to the classic indicators that considers only vehicle-vehicle interactions (such as Crash Potential Index, Rate Deceleration to Avoid Crash, Available Maximum Deceleration Rate, Time to Collision,etc..).
First results are very promising and the developed software can be used as an add-on for common used microsimulation packages such as Vissim and Aimsun and Tritone, and the software works on Windows, MacOS and Linux. Conclusions are that the methodology allows to find the critical points of a network through microsimulation and allow to consider the flow and the detail geometry of the network for safety analysis. This model can consider road-side objects without perturbation of trajectories road side object cannot be considered. And for the end, it is fast, effective and free, everyone can try it.

Davide Shingo Usami, Luca Persia and Veronica Sgarra- Determinants Of The Use Of Safety Restraint Systems In Italy / The Independent Design Verification Engineer (DVE) plays a vital role in supporting local authorities to meet their statutory duty under internal planning acts or strategic planning programmes. Mainly appointed to verify compliance of Contractor’s design scope of work with Employer’s requirements, the DVE ensures high standards of design, since verified following objective criteria and an impartial evaluation process. Above all, while the designer must remain responsible for the design, the reviewer must be satisfied with the compliance of design with principles and assumptions, along with the adequacy of the functional and safety targets of the Project [1].
In many countries the DVE in civil and transport industry impacts on the life-cycle of a Project in a relevant way: primarily allows to supervise the global coherence of the design and the technical feasibility of the work, its operation and maintenance, avoiding or minimizing variation works. In Italy, for the same reason, the Design Verification is mandatory by law – as per Leg. Decree 50/2016 Art. 26.
The purpose of this paper, indeed, is to make clear how DVE allows increasing the confidence for the “constructability” of the design and hopefully reducing the costs associated with it. In particular, the economic impact of the DVE on each stage of the Chain Design and how it enables to improve the management of Works will be discussed.
As an example, the appraisal framework of Line 3-Riyadh Metro Project will be presented, this under the procedure of verification, highlighting why a longer relation of trust, reliability and strong communication between involved parties is reached, thanks to the continuous support and interface of the Independent Engineer with project Stakeholders. Finally, as outcomes of the consolidated expertise of Italcertifer in managing DVE services, an analysis on how a design error affects time and costs will be given.

Michela Bonera and Giulio Maternini- Methodology for the application of predictive method for road safety analysis in urban areas. The case study of Brescia / Road infrastructure is commonly considered as a core factor of road accidents phenomenon and, for this reason, it is essential to monitor existing roads and evaluate their projects to ensure high safety standards for users. Within the context of road safety analysis, the Highway Safety Manual (HSM) represents the main reference at international level. In particular, the American experience has led to an innovative approach for road safety analysis, that is the predictive method. It is based on a complex quantitative statistical model that produces an estimate of the expected variation of the number of accidents, of their severity and their typology, based on correlations existing among road fatalities and road geometrical characteristics, traffic flow condition, whole set of accident records and other specific parameters.
Considering the predictive method as an extremely useful tool to perform road accident analysis, the authors applied this approach to a context typical of European middle-size cities which is highly different from that of American urban areas, on which the predictive method has been developed. The research assumes as the case study the city of Brescia (Italy) and opportunely adjusting some of the coefficients related to the Safety Performance Function (SPF) and Crash Modification Factors (CMFs) developed in the original structure of the Highway Safety Manual, it has been possible to demonstrate how the predictive method of the HSM can be applied in a different context than the American one.
The results obtained with the modified structure would show a slight deviation from the real data related to road accidents occurring in the study area of Brescia Via Milano. Therefore, in order to validate the methodology proposed in this research, it would be necessary to perform further analysis and tests, also on other case studies. The values resulting from the calibration performed for Brescia return -8% error compared to the actual collisions of the 3 years period observed with a total of 5.941 crashes in 3 years and an average of 1.830 crash/year.

Conclusions are that the prediction method represent a strong effective tool to esteem effective collision occurrence, as an ex-ante measure of road safety analysis. In particular, an interesting outcome returned from the comparison between the 2 computations although:

-this work can be accounted within the first attempts to test the transferability of the method to an Italian urban site of Minicipality of Brescia but just injuries and fatalities (FI) collisions were accounted due to the data availability

-the CMFs were modified as less as possible, according to the site condition, in order to obtain a more reliable estimate of the average crash frequency for the context.

Considering limits and future developments that it would be useful to extend the method over several sites which registered enough number f collisions, in order to obtain a more reliable estimate of the model and also, an average percentage of PDO could be gathered from the insurance companies.

Stefano Carrese, Marco Petrelli and Alessandra Renna- Safety at LCs in Italy: evidence from the Safer-LC Project / In railways one of the most critical point is represented by the intersections with road, especially at level crossings, where the interaction between road users (cyclists, pedestrians, motorcyclists, drivers, etc.) and train users might generate conflicts and risk situations. Level crossing accidents represent 24% of all significant railway accidents when railway suicides are excluded according to the ERA (European Union Agency for Railways) statistics. There is a complex interaction among the components that makes this kind of intersection dangerous, depending on the road users’ behaviour, the unsafe layout of the infrastructure and the response of the various type of users with regard to the different conditions (traffic, weather, design, etc.).
Starting from these considerations, the Safer-LC Project has the objective of upgrading safety and minimising risks at and around level crossings by developing a fully integrated cross-modal set of innovative solutions and tools for the proactive management and new design of level-crossing infrastructure.
This paper presents the results of the first phase of this project with special attention about the results of the Italian level crossings conditions. With regard to the first phase of the project, the paper proposes a comparative analysis between Italy and other six European countries (Greece, Finland, France, Italy, Norway, Spain and Turkey), carrying out an in-depth Level Crossing accident analysis with data and reports from the railway operators and the national accident investigation bodies. The analysis focuses the attention on specific variables such as details on collision, victim, road and railway environment, level crossing characteristics and circumstances. The analysis highlights the existence of some critical issues for safety with important differences in terms of characteristics and intensity in each country and especially for the Italian case.

Nicola Baldo and Matteo Miani- Safety Performance Functions for road intersections in the Friuli Venezia Giulia Region / Road accidents are one of the top 10 causes of mortality in the world. The safety of a road infrastructure is closely linked to the number of accidents that occur on it and the severity of the consequences that come from it. Nevertheless, road accidents are rare and unpredictable events and the knowledge of its number, occurred in a given period of time, is not sufficient to represent the safety level of a road element. Safety Performance Functions (SPFs) are an important analysis tool, applicable in project practice and in the intervention planning: SPFs seek to identify an empirical relation between the occurrence of the crash event and the multiplicity of factors that affect the road environment, with the aim of develop predictive mathematical models.
The aim of this paper was developing SPFs of four different types of road intersections: unsignalized three-leg intersection (3ST), unsignalized four-leg intersection (4ST), signalized three-leg intersections (3SG), signalized four-leg intersection (4SG). The data on accidents and traffic volume of 28 intersections, which are under the jurisdiction of Friuli Venezia Giulia Road S.p.A., were collected and analyzed. To model the empirical relation between crash frequency and traffic volume, a feed-forward artificial neural network (ANN), characterized by the hyperbolic tangent transfer function and one hidden layer, was used.
SPFs of the analyzed road intersections have shown a slope reduction of the tangent line when annual average daily traffic increased on the main leg, namely, the road capacity is not able to meet the increase in the volume of traffic. As a result, this leads to a saturation that induces slowdowns with a lower probability of running into an accident. Moreover, considering the same traffic volume, signalized intersections have shown a greater crash frequency than unsignalized intersections.

The presenter concluded that the artificial network approach has allowed to identify the analytical expression of the model and the implemented feedforward neural network is composed of 3 layers, with three neurons for the input layer and two input for the hidden layer. However, a comparison between the predictive models (HSM vs ANN) has shown differences that can’t be neglected.

CHAIRMAN: Chiara Gruden