Browsing by Subject "Roundabouts"
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Item Effect of Signing and Lane Markings on the Safety of a Two-Lane Roundabout(Minnesota Department of Transportation, 2014-01) Hourdos, John; Richfield, Veronica; Acosta, LuzcenitThis report presents a study of the impact lane markings and signing have on driving behavior at a two-lane roundabout located in Richfield, Minnesota. After its completion in 2008, this roundabout sustained a suspiciously high amount of crashes. In response, through this study, engineers experimented with changes in the roundabout’s signs and lane markings, as roundabout design regulations are relatively lax and nonspecific in contrast to those for standard signalized intersections. An observational study was conducted that reduced 216 hours of before and after video records of the roundabout into a database of all the violations committed by drivers. Along with the observational data, crash records were analyzed and demonstrated that improper turns and failing to properly yield account for the majority of collisions. The changes implemented in the approaches to the roundabout and specifically the extension of the solid line seems to have reinforced the message to the drivers that they must select the correct lane before approaching the roundabout entrance. Although choosing the correct lane does not directly address yielding violations, it does reduce the occurrence of drivers conducting an improper turn and to some extent reduces the need for a driver to change lanes within the roundabout. The implemented changes produced a 48% reduction in normalized occurrences of improper turns, and a 53% reduction in normalized occurrences of drivers choosing the incorrect lane a month after the changes, while a year later, these reductions were 44% and 50%, respectively.Item Evaluation of Safety and Mobility of Two-Lane Roundabouts(Minnesota Department of Transportation, 2017-07) Hourdos, John; Parikh, GordonWhen looking at measures of fatal and severe-injury crashes, roundabouts have demonstrated improved safety performance compared to traditional signalized intersections. Despite this, when it comes to less severe crashes, multilane roundabouts fail to provide a similar benefit. Previous research into this topic has identified behaviors that are associated with crashes in two-lane roundabouts, with yielding violations and turn violations generally being the largest contributors to crashes. This study sought to build on that work by expanding the data collection effort to include more sites and relate the frequency of individual behaviors to specific design features. Ultimately, four roundabouts were chosen for data collection and analysis, with two of them being full 2x2 roundabouts and the other two half-2x2. These locations were University Dr. S and 5th Ave. S in St. Cloud (half-2x2), 185th St. W and Kenwood Trail in Lakeville (full-2x2), and TH-22 and Adams St. (half-2x2) and TH-22 and Madison Ave. in Mankato (full-2x2). In the last two, changes in traffic control were implemented to reduce failure-to-yield crashes, and the study compared the driver behavior before and after the interventions. In general, the collective results show that the problems observed in the earlier site are present in all of the other sites with scale variations prompted by geometric and traffic control design elements. For example, in the St. Cloud roundabout, an increased rate of right-from-inner-lane turn violations were observed, which can be attributed to the sharper deflection angles present. Additionally, from the aforementioned roundabout as well as the one in Lakeville, it was concluded that turn violation rates are affected on the single or multilane geometry of the links approaching the roundabout. Single-lane roads result in fewer left-from-outer-lane violations. Overhead lane designation signs result in reduced turn violations similar to the earlier studies’ interventions in the approach lane markings. Unfortunately, apart from confirming the trend, no successful design or intervention was discovered regarding yield violationsItem Investigation of Pedestrian/Bicyclist Risk in Minnesota Roundabout Crossings(Minnesota Department of Transportation, 2012-09) Hourdos, John; Richfield, Veronica; Shauer, MelissaMany cities in the United States are installing roundabouts instead of traditional intersections, due to evidence that roundabouts dramatically reduce fatal and severe injury crashes compared to traditional signalized intersections. However, the impact on pedestrian safety is not clear. This project was developed to investigate pedestrian accessibility in Minnesota urban roundabouts, addressing complaints from pedestrians regarding difficulties in crossing and safety. The methodology followed in this ongoing research is typical of other observational studies. A sufficiently large number of observations on the interactions between pedestrians or bicycles (peds/bikes) and vehicles at two modern urban roundabouts in the Twin Cities of Minneapolis and St. Paul in Minnesota were collected and reduced. These observations have supported a two phased analysis. Phase 1 involved the extraction of general information describing the crossing event, such as who yielded, the location of the crossing, or the number of subjects involved. Phase 2 looked deeper into these factors by considering the conditions inside the roundabout before the vehicle proceeds to the crossing and meets with the ped/bike. The results presented, although containing no surprises, do highlight and categorize the existence of friction between pedestrians and drivers at roundabout crossings. Also the identification of factors affecting driver yield behavior and pedestrian wait time do offer good background for modeling such interactions.Item The Optimal Fit: Accommodating Trucks in Roundabouts(Transportation Engineering and Road Research Alliance (TERRA), 2013-07) Transportation Engineering and Road Research Alliance (TERRA)This 2-page fact sheet provides information about the impact on trucks entering roundabouts, recommended design parameters for two-lane roundabouts, and related studies.Item Roadway Safety Institute News (Spring 2016, vol. 3, no. 2)(Center for Transportation Studies, University of Minnesota, 2016) Roadway Safety Institute (RSI)Articles include: Study finds higher crash risk for truckers with untreated sleep apnea; Improving safety of two-lane roundabouts; Visit puts focus on distracted driving research; Researcher spotlight: Lee Munnich; Researcher spotlight: John Hourdos; Education efforts promote STEM to underrepresented groups; RSI researcher shares expertise on teen drivingItem Video Detection and Classification of Pedestrian Events at Roundabouts and Crosswalks(Intelligent Transportation Systems Institute, Center for Transportation Studies, 2013-08) Morris, Ted; Li, Xinyan; Morellas, Vassilios; Papanikolopoulos, NikosA well-established technique for studying pedestrian safety is based on reducing data from video-based in-situ observation. The extraction and cataloging from recorded video of pedestrian crossing events has largely been achieved manually. Although the manual methods are generally reliable, they are extremely time-consuming. As a result, more detailed, encompassing site studies are not practical unless the mining for these events can be automated. The study investigated such a tool based on utilizing a novel image processing algorithm recently developed for the extraction of human activities in complex scenes. No human intervention other than defining regions of interest for approaching vehicles and the pedestrian crossing areas was required. The output quantified general event indicators—such as pedestrian wait time, and crossing time and vehicle-pedestrian yield behaviors. Such data can then be used to guide more detailed analyses of the events to study potential vehicle-pedestrian conflicts and their causal effects. The evaluation was done using an extensive set of multi-camera video recordings collected at roundabouts. The tool can be used to support other pedestrian safety research where extracting potential pedestrian-vehicle conflicts from video are required, for example at crosswalks at urban signalized and uncontrolled intersections.