Dražen Cvitanić

Impact of exclusive bus lane on urban arterial performance measures

The introduction of an exclusive bus lane can be one of the operational measures that will improve the quality of public transport, especially on urban arterials with intense traffic flows. By using an exclusive traffic lane, buses can reduce their travel time and increase speed, resulting in a more efficient public transport, better level of service and satisfied passengers. However, the change of an existing traffic lane into a bus lane may have an impact on the quality of traffic on the adjacent lanes and the arterial as a whole. So, it is necessary to analyse and evaluate this impact before implementing a new mode of traffic regulation. This paper presents a traffic analysis of the possibilities of changing the curb traffic lane into a bus-only lane on an arterial street in Split. Using the calibrated simulation model, the average speeds, travel times and average intersection delays were compared for variants with and without a bus lane. Field data were used for performing simulations, and additionally, variants with increased traffic volume were also tested. Based on the obtained results, i.e. the performance measures of arterial and intersections level of service, comments and a conclusion were provided regarding the possibility and purpose of introducing the bus lane in terms of the impact on the traffic flow quality.

Istraživanje postotka vremena provedenog u koloni na dvotračnim izvangradskim cestama

Dvotračne izvangradske ceste u Bosni i Hercegovini čine najveći postotak cestovne mreže pa preuzimaju gotovo cjelokupan teretni promet. Zbog toga se na njima često stvaraju kolone, brzine vozila se smanjuju i gustoća prometa raste. Za poboljšanje kvalitete odvijanja prometa potrebno je utvrditi razinu usluge za postojeće stanje te za alternativne mogućnosti rekonstrukcije kritičnih elemenata cestovne mreže. U radu se istraživao postotak vremena provedenog u koloni kao primjerena mjera za određivanje efikasnosti izvangradskih dvotračnih cesta.

Detection and analysis of hazardous locations on roads: a case study of the Croatian motorway A1

The present paper describes research undertaken to identify causes underlying single-vehicle accidents (in terms of road design, driver behaviour and vehicle handling characteristics), which continuously happen in one specific section of Croatian motorway A1. The research resulted in a proposed procedure for a detection of hazardous locations on motorways and analysis of possible causes of single-vehicle accidents. The main part of the procedure involves test-rides with a vehicle equipped with devices (a ball bank indicator and a GPS data logger), which collect data on driver’s behaviour and vehicle handling characteristics (position, speed, longitudinal and lateral acceleration, heading, path radius, etc.). Despite the fact that the motorway was designed in accordance with the design guidelines, test rides performed by higher operating speeds identified two locations with a lateral acceleration change a few times higher than the design value. The collected data are then used for analysing hypotheses about the possible causes of accidents by using a vehicle dynamic model. The hypothesis that a sudden change in lateral acceleration could result in a driver’s inadequate manoeuvre like braking and cause a vehicle accident was analysed with a transient bicycle model. The results of test rides and the transient bicycle model indicate that speed, intensity of deceleration and underinflated tires significantly affect the probability of a single-vehicle accident. First published online 31 January 2017

Operating speed models of two-lane rural state roads developed on continuous speed data

This paper presents models for predicting operating speeds on tangent sections and curves of two-lane rural roads developed on continuous speed data. The data corresponds to 20 drivers of different ages and driving experiences, driving their own cars along an 18 km long section of a state road. The data were first used for determination of minimum operating speeds on curves and maximum operating speeds on tangents and their comparison with speeds in the middle of curves and tangents i.e. speed data used in most of the operating speed studies. There was no significant difference between speed models developed using speed data in the middle of tangents and curves and models developed using maximum and minimum operating speeds on tangents and curves. Models developed on continuous data have higher coefficient of determination than models developed on spot speed data. It can be concluded that the method of measuring has more significant impact on the quality of speed model than the location of measurement.