Goran Zovak

Turbo Roundabouts: A Brief Safety, Efficiency and Geometry Design Review

The application popularity of various roundabout types around the world has driven substantial efforts to optimize their geometry design. Implementing effective roundabouts requires optimizing traffic safety (TS) and traffic (operational) efficiency (TE) while considering various geometry and other factors. In multi-lane roundabouts driver indecision and misunderstanding of the driving rules and situations can lead to weaving conflicts and accidents. These accidents are frequent and often affect TS and TE. The turbo roundabout concept has emerged as a possible alternative to conventional multi-lane roundabouts, aiming to improve exclusively TS. However, some studies do not allow definitive conclusions about their TE (capacity) influence. To capture a relationship between turbo roundabout design, TS and TE parameters brief overview of the latest guidelines and studies is presented here.

The Driver Behaviour and Impact of Speed on Road Safety on the Motorways in Croatia

The paper presents the current research related to the speed of traffic flow on the roads of high serviceability. It analyses the speed of vehicle as one of the main causes of traffic accidents. A flat four-lane motorway section, motorway section in the tunnel and a city bypass section were chosen for this research, and several speed limit scenarios for the vehicles have been applied with the aid of variable signalling. The survey results show that few vehicles respect the speed limits in traffic in the case of a straight section of motorway or city stretch of the motorway which has good geometric elements; however, speed limits are exceptionally well respected in tunnels. Although a large number of drivers do not respect the signs, a certain group of drivers can be influenced by variable signs of limitations, and thus positive changes can be achieved in traffic flow which will result in increasing the traffic safety on the motorways. Thus, increasing the degree of respect for speed limits on the motorways directly affects the increase in the level of traffic safety. It is necessary to influence the group of drivers who do not respect the speed limits with other measures, including repressive ones.

Empirical Approach for Determining Lane Change Distance at Obstacle Avoidance Manoeuvre

The lane change of vehicles for avoiding hitting a sudden obstacle represents a significant and unique problem for traffic accident experts. Most mathematic models for determining the lane change distance are based on theoretical research studies and a lot of simplifications and approximations. In order to analyse the influence of different drivers and vehicles on a manoeuvre, an experimental research study of lane change was carried out at the test track which enables repeatability in the same conditions. The drivers were instructed to drive through the test track at a maximum speed without displacing the traffic cones. Based on the statistical analyses of the successful lane change manoeuvres an empirical model for the calculation of lane change distance for obstacle avoidance was formed. This model can be applied in the procedure of traffic accident reconstructions as well as within the development of the concept of modern intelligent vehicles.

Application of standards in auditing of stations for technical inspection of vehicles

The HRN EN ISO/IEC 17020:2005 requirements have been applied to the auditing of the operation of the stations for technical inspection of vehicles which, as part of the system of technical inspections and registration of vehicles in the Republic of Croatia is carried out by the Croatian Automobile Club, based on the public accreditation issued by the Ministry of the Interior of the Republic of Croatia. The direct consequence of the application of this standard, i. e. the implementation of the quality management system is the improvement of the quality and efficiency in performing the respective activity, thus raising the level of technical roadworthiness of vehicles, i. e. traffic safety on the roads in the Republic of Croatia. KEY WORDS: supervisory/inspection bodies, quality, quality management, technical inspection of vehicles, auditing

INFORMATION SYSTEM ON ROAD CONDITIONS IN CROATIA - PLANS OF DEVELOPMENT

The quality of information about road conditions in theRepublic of Croatia do nor meet the needs of their users- roadvehicle mororists, regarding their content, updating criteria andtimely announcement and warning of potential risks for thedrivers. Neither do they meet the criteria of monitoring and supportduring poor traffic and weather conditions. The paper considerscritically the cwTent situation in the information systemabout the road conditions in the Republic of Croatia, and studiesthe reasons for such a condition. It also gives guidelines forimproving the level of quality of this service and the plans for itsdevelopment. It mentions the activities that should be carriedout in order to improve the whole information system regardingupgrading oft he current system in the segments of receiving anddistributing information, application of new technical andtechnological solutions (CPS, RDS, TMC), development andimprovement of the information and communication infrastructure,data exchange network, introduction of navigationsystems, etc.