THE IMPACT APPRAISAL OF THE TRAFFIC LANE USE CONTROL SYSTEM OF THE KALLA BRIDGES

The impact appraisal of the traffic lane use control system of the Kalla bridges has been conducted as a part of the Research and Development Programme on ITS Infrastructures (TETRA) financed by the Ministry of Transport and Communications. The long-term effects of the Kalla bridges telematics project, which was implemented in the year 1995, have been examined in the work and the applicability of the Impact Appraisal Guidelines of Telematics Projects on examining the long-term effects has been tested. The before-after studies of the Kalla bridges variable traffic control system were prepared in the years 1994 and 1995, and now in the year 1999 a similar study was conducted. These studies were compared to each other so that the long-term effects of the traffic control system could be examined. The research part included about an hour of video monitoring of the operation of the variable traffic control devices which are in use during the service breaks of the Kalla liftbridges. In addition, the traffic flows were counted at four points. The video monitoring was done in the beginning of June by using seven video cameras. At the same time, the licence numbers of the vehicles bypassing the control system were collected for a postal questionnaire. When comparing the current research results to previous research, the changes in driving speeds and the queue build-up were found to be relatively small. A significant change had occurred in following the vehicle signals indicating lane closures. They were followed well in the year 1995 but now a share of 3% of the drivers were driving in the passing lane despite the vehicle signals indicating a lane closure. The drivers had a significantly more positive opinion about the signalling system than previously. The implementation costs of the system have been about 4.1 million FIM and annual maintenance costs have been about 50,000 FIM. The most significant technical problems have been due to damage caused by thunderstorms. The lifting of the bridges for waterway traffic as well as for service works will cause an annual cost of 790,000 FIM because of delays to vehicle traffic. On the other hand, the control system will improve the safety of service works and will reduce the time spent on them by about 9.5 hours per service break. Traffic safety on the road segment has had a positive development which can partly be due to the variable lane use control system. However, the main reason for the reduction in the number of accidents can be the use of variable speed limits during the peak hours of traffic and in bad weather conditions on the same road segment. The traffic control system can mainly be considered profitable due to improved working safety. The study has been granted European Community support in the field of Trans-European Networks - Transport.