The investıgatıon of roundabouts in terms of capacıty and traffıc safety

viTHE INVESTIGATION OF ROUNDABOUTSIN TERMS OF CAPACITY AND TRAFFIC SAFETY(M.Sc. Thesis)Efkan YÜKSELGAZİ UNIVERSITYINSTITUTE OF SCIENCE AND TECHNOLOGYJanuary 2007ABSTRACTIn our country, passenger and freigh transportation have been realized by roadtransportation heavly. As a natural result of unbalanced transportation andheavy traffic burden of road intrastracture, traffic accidents frequently occuredon road. According to the conclisions of statistical studies, % 47 of injury andfatality accidents on urban roads and %37 of rural roads happened atintersections. In European country % 27 of road accidents and % 10 of totalfatal traffic accidents occur at the intersections [1,2].Improperly designed intersections and intersections which are not regulated tofunction safely without specific standards constitute the black spots in Turkey.From these two points it can be inferred that first of all, the definition of basicneeds and demands of highway and intersection users, the balancing of capacityand safety parameters , the formation of highway and intersectioninfrastructure suitable for this balance are the reasonable technical approachesto traffic safety.Several features of roundabouts promote safety. A good designed roundaboutsprevents high driving speeds, reduced the number of conflicts and decreasesviispeed differences and variations in effect caused by mass and direction. Attraditional intersections with stop signs or traffic signals, some of the mostcommon types of crashes are right-angle, left-turn, and head-on . These types ofcollisions can be severe because vehicles may be traveling through theintersection at high speeds. With roundabouts, these types of potentially seriouscrashes essentially are eliminated because vehicles travel in the same direction.Installing roundabouts in place of traffic signals and non control intersectionscan also reduce the likelihood of rear-end crashes and their severity byremoving the incentive for drivers to speed up as they approach green lights andby reducing abrupt stops at red lights.This thesis study examines decision making process in designing andmaintenance of roundabouts the traffic and safety parameters of thesestructures.Science Code : 911.1.134Key Words : Modern RoundaboutsPage Number : 154Adviser : Dr. Nihat EROĞLU