The simulation analysis of suppressed traffic

Mathematical models of transportation systems have played an important role in transportation planning in agglomerations. These models state the hypotheses of how people use transport systems and gives information how users respond to changes in the transportation systems. One of the issue connected with estimation of traffic infrastructure effectiveness is assessment of implementation period effect, when streets or public transport modes work under unusual conditions-street closure, detours, temporary lack of tram connection etc. As a result of such situation there is completely different scheme of traffic and PT connections which imply on modal split, assignment and of course on level of demand. In the paper are presented the results of questionnaire surveys conducted on the subject of roundabout in Krakow. Due to reconstruction of the existing roundabout to the three-level road junction, significant impediments to the traffic scheme have occurred. The main aim of the questionnaire was to define the impact of impediments on the travel behaviour of drivers on the demand level. Thus, it was possible to define changes in demand, trip distribution and trip assignment. The results of the survey state are the basis for calculation of demand elasticity rate. For the purpose of the analysis, the assignment was calculated with a simulation model of the city (calibrated in VISUM software). It was possible to quantify the impact of reduced traffic by changes of vehicle kilometres and vehicle hours on the street network, both in the area of direct impact of the traffic limitations and in the whole city. The same analysis was done for models of fixed demand and it was possible to compare impact of reduced traffic on traffic conditions in the city. The results of traffic research carried out during the reconstruction of the roundabout named Ofiar Katynia in Krakow will be presented in this paper.