DETECTION AND ASSESSMENT OF SAFETY PROBLEMS WITHIN ROAD TRANSPORT DECISION MAKING Prof. Dr. Nikolay Georgiev eng. Violina Velyova ‘Todor Kableshkov’ University of Transport, Sofia, Bulgaria

Traffic Safety Problems and Specifics The transportation system safety in many countries often constitutes the largest public- sector problem. The transportation system safety in many countries often constitutes the largest public- sector problem. This problem is characterized by the presence of a variety of potential negative events that could occur (including their causal factors, complexity of their identification and stochastic nature of their consequences). This problem is characterized by the presence of a variety of potential negative events that could occur (including their causal factors, complexity of their identification and stochastic nature of their consequences). The planning and management process concerning traffic safety requires that engineers collect and maintain traffic safety data, identify hazardous locations, conduct engineering studies, and establish project priorities. The planning and management process concerning traffic safety requires that engineers collect and maintain traffic safety data, identify hazardous locations, conduct engineering studies, and establish project priorities.

1. Main Purposes of the Article IDENTIFICATION OF FACTORS AFFECTING TRAFFIC SAFETY IDENTIFICATION OF FACTORS AFFECTING TRAFFIC SAFETY DEFINING THE PROCEDURE FOR SAFETY MANAGEMENT DEFINING THE PROCEDURE FOR SAFETY MANAGEMENT SELECTING AND ADAPTING ACCIDENT PREDICTION MODELS FOR TRAFFIC SAFETY MANAGEMENT SELECTING AND ADAPTING ACCIDENT PREDICTION MODELS FOR TRAFFIC SAFETY MANAGEMENT

2. IDENTIFICATION OF FACTORS AFFECTING TRAFFIC SAFETY The operating environment of potential conflicts between traffic participants could be result of the influence of a great number of factors. Key factors affecting operating environment and safety: - state and/or local policy on road safety; - characteristics of traffic flow (traffic intensity, speed, density and structure; - vehicle characteristics and human behavior; - weather conditions; - infrastructure characteristics; - traffic management, etc.

Factors affecting operating safety connected with the traffic conditions and infrastructure elements are called engineering factors They are technical and technological factors which can be divided into 6 main groups: - road segment or intersection characteristics (length of the road segment, number of lines, traffic volume, etc.) - alignment (vertical or horizontal) - road shoulder type and width - infrastructure characteristics (side ditches, barriers, fences, etc.) - devices for traffic control (road signs, road markings) - technological factors such as traffic management. Engineering factors are exactly those which are of main importance because they can be changed to a certain extent and therefore managed. 2. IDENTIFICATION OF FACTORS AFFECTING TRAFFIC SAFETY

3. DEFINING THE PROCEDURE FOR SAFETY MANAGEMENT

4. SELECTING AND ADAPTING ACCIDENT PREDICTION MODELS Where: – estimated number of accidents (dependent variable); - independent variables of the model; - coefficients of the equation to be estimated by the model.

Initially 14 causal factors (model variables) have been considered and analysed by the usage of multi factor analysis. Subsequently, some of them have been estimated as very poorly influencing factors and excluded from the model. Analysed: - -average daily traffic (vehicles/day) on the major road and on the minor road; - - lane number of the major road and of the minor road; - - lane width (in meters) of the major road and of the minor road; - - existence of separate lanes for right turn of the major road and of the minor road. 4. SELECTING AND ADAPTING ACCIDENT PREDICTION MODELS

Model 1: Road accidents with fatalities on four-leg signalized intersections: - predicted number of road accidents with fatalities for four-leg signalized intersections; - independent variables of the model; – coefficients of the model to be estimated. X 1 and X 2 - average daily traffic (vehicles/day) on the major road and on the minor road; X 3 and X 4 - lane number of the major road and of the minor road; X 5 and X 6 - lane width (in meters) of the major road and of the minor road; X 7 and X 8 - existence of separate lanes for right turn of the major road and of the minor road..

76 four-leg signalized intersections in Sofia: Y-follows lognormal distribution with large value of its mean Estimation procedure -> Lognormal regression model ->least squares method

Model 2: Road accidents with fatalities on three-leg stop/ signalized intersections 60 three-leg stop controlled intersections in Sofia: Y-follows lognormal distribution with large value of its mean Estimation procedure -> Lognormal regression model ->least squares method

CONCLUSION The proposed procedure and accident prediction models could be successfully used in decision making to improve traffic safety in cities where it is required to estimate the potential number of accidents that are expected to occur at a certain intersection. By the definition of the main technical and technological factors affecting safety and collection of needed statistical information, traffic safety can be seriously improved which will result in a general reduction of road accidents number and their consequences (fatalities, injuries, material loss).

Thank you for your attention!