This paper will try to present some of the causes which resultin vibrations during the train movement. Vibrations originateat the contact point between the undercarriage and thetracks. Theoretical analysis has been done of determining thespectral density of the acceleration process - vibrations of thenon-suspended and suspended locomotive mass, and then thevibrations of diesel electric locomotive type Hi 2061 weremeasured in different morphological conditions and geometricalstate of the track at different speeds. Based on the correlationand spectral analysis of the measured accelerations- vibrations,conclusions can be made about the condition of the trackand of the non-suspended mass of the locomotive. It should bestressed that determining the nature of vibrations is in the functionof determining the system reliability. If it refers to the trainand track in exploitation, the life time can be predicted, i.e. theoverhaul can be planned, and if it refers to the development,then we can use the results as the basis to determine modificationsand improvements.The efficiency of applying fuzzy logic in controlling the trainride with various input variables has been presented, where specialemphasis is put on the input variable which provides uswith the data on vibrations parameter. The analysis of vibrationsacting on the system, and the processing of the vibrationsparameter and the use of fuzzy logic provide us with the possibilityof controlling the train power plant.

Single-lane roundabouts may face the problems of gettingcrowded and empty in their circulatory roadway due to a strongstream of pedestrians and/or cyclists.Vehicles at the roundabout entries or exits have to providethe right of way over pedestrians and/or cyclists. Therefore, itcomes to disturbances and traffic jams.If there are jams at the entry carriageway, vehicles are unableto get into roundabouts. If there are jams at the exit carriageway,vehicles are not able to leave the roundabout. U'henthe length of vehicle platoon at the exit is so long that it reachesthe preceding entry, the roundabouts suffer from getting fullyovercrowded.The paper presents the methodology of calculating the reductionof the roundabout capacity due to the pedestrian or cycliststream.The method of calculating the reduction of the roundaboutcapacity with the disturbed streams may be used for roundaboutsin urban environments, where the strength of the cyclistor pedestrian streams is not negligible.

Traffic planners and designers are daily confronted by theproblems of traffic flow. Finding a solution for the optimal organisationof the traffic system in the wider (at the state level)and the narrower sense (cities, towns), requires accurate planningand adequate financing. With Croatia being a developingcountry that has higher investments into the traffic system, thematerial means need to be rati01~t~lised and the human andland resources cautiously managed. With the development andimplementation of the traffic studies, an improvement of thetraffic in cities can be expected. The work describes the trafficmeasures which provide higher quality traffic flow, with low investments.They can be used as guidelines in planning the trafficand as the first implementations of solutions from the trafficstudies.

The paper deals with criteria and procedures in evaluationof timely preventive maintenance recommendations that willsupport continued safe operation of aging jet transports untiltheir retirement from service. The active service life of commercialaircraft has increased in recent years as a result of low fuelcost, and increasing costs and delivery times for fleet replacements.Air transport industry consensus is that older jet transportswill continue in service despite anticipated substantial increasesin required maintenance. Design concepts, supportedby testing, have worked well due to the system that is used to ensureflying safety. Continuing structural integrity by inspectionand overhaul recommendation above the level contained inmaintenance and service bulletins is additional requirement, insuch cases. Airplane structural safety depends on the performanceof all participants in the system and the responsibility forsafety cannot be delegated to a single participant. This systemhas three major participants: the manufacturers who design,build and support airplanes in service, the airlines who operate,inspect and mantain airplanes and the airworthiness authoritieswho establish rules and regulations, approve the design andpromote airline maintenance performance.

The paper presents the solution for the modification of thebrakes on the electric railcar series 6111 used in suburban traffic.It also gives the results of the performed measurements aswell as their analysis.The mentioned electric railcar is fitted with air and rheostaticbrakes whose activation is mutually independent. Sincesuburban traffic means frequent slopping, and since the enginedriver does not use the rheostatic brake regularly, but only theair brake, the wear of the brake lining and wheels is higher, andthe heat load on the brake elements is substantial. By regularapplication of rheostatic brake, the air brake could be LLSed lessthus contributing to a lower wear of the friction elements.The presented solution for the modification of the brakeconsists of co-ordinated and automatic action of the rheostaticand air brake with every braking

The paper presents decomposition analysis of road transpOI·tation system using the ergonomic system ana~vsis. Theanalysis is performed by its 'Man-Vehicle', 'Man-Road' and'Man-Operation' subsystems treated as systems with their ownsubsystems.Since the ergonomic factors within road transportation systemwith its subsystems or elements are very complex and comprehensive,only the implications of the 'Driver-Vehicle' systemare analysed.

The paper studies the possibility of constntction of a newrailway track section from the existing stop Gradec on the railwayline Zagreb - Koprivnica to the railway station Sveti !vanZabno on the railway line Kriievci - Bjelovar, thus improvingthe importance of the Bjelovar region and shortening the routeto Osijek by 16.5 km.