2013 Session: 626

• Emission Estimation at Multilane Roundabouts: Effect of Movement and Approach Lane
  Abstract: This research explores the effect of multilane roundabouts located on urban corridors on traffic performance and pollutant emissions generated from vehicles. It further compares the emission of vehicles moving through the roundabout as they use either the entry left or right lane. The paper uses the speed trajectories from a field data collection at four multi-lane roundabouts in Aveiro, Portugal. To estimate the second-by-second emission generated from the vehicle during different acceleration-deceleration cycles, the "Vehicle Specific Power" (VSP) emission methodology is applied. This paper also develops predictive models using congestion-specific vehicle speed profiles for two-lane roundabout approaches. The paper further implements the predictive models and second-by-second speed trajectories to compare the emission generated from a vehicle entering the roundabout using right lane with a vehicle entering the roundabout using left lane. The hypothesis is that right lane and left lane may have different flow rate and may face different conflicting circulating flow; therefore, their emission rates might be different.This paper tests the hypotheses that difference in; a) lane flow (left v.s. right lane); b) conflicting flow for left and right lane; and c) overall congestion level effects the emission amounts generated from vehicles in each lane. Under low congestion levels vehicles in right lane emit more pollutant because they have on average higher speeds and sharper acceleration and deceleration rates. For high congestion levels if flow rates for left and right are equal, vehicles in left lane produce more emission because vehicles in left lane experience longer stop-and-go cycles and have different speed trajectory than vehicles in right lane.
  Authors: Salamati, Katy; Coelho, Margarida Cabrita; Fernandes, Paulo Jorge; Rouphail, Nagui M.; Frey, H. Christopher; Bandeira, Jorge
  Authors: Salamati, Katy; Coelho, Margarida Cabrita; Fernandes, Paulo Jorge; Rouphail, Nagui M.; Frey, H. Christopher; Bandeira, Jorge
  Year: 2013
  Document Type: Paper
  Subject: Design; Operations and Traffic Management; Safety and Human Factors
  Session: 626
  Paper Number: 13-0420
• Detailed Driver Behavior Analysis and Trajectory Interpretation at Roundabouts Using Computer Vision Data
  Abstract: With recent and important upgrades to North American intersection design guides, roundabouts are gaining popularity as a method of reducing road conflicts, streamlining flow, and curbing excessive speeding of busy intersections. The current design approach, however, makes use of spot-mean speed measures and design criteria which do not take into account yielding behaviour and acceleration/deceleration which may be affected by regional driving culture and local roundabout design.This research paper introduces the methodology being developed for the detailed analysis of driving behaviour, trajectory interpretation, and conflict measures in modern North American roundabouts from video data extracted by means of computer vision. The analysis explores the methods used to prepare microscopic speed maps, compiled speed profiles, lane-change counts, and gap time measures. It also introduces and discusses the interpretation of trajectories at the scale of roundabout merge sections instead of looking at safety from the point of view of a roundabout as a unified system.The research finds significant variation in distributions of speed across five case study roundabouts in the province of Québec, Canada which may be explained by regional differences in design and road use. It also reports aggressive gap times and polarised (uneven) traffic flow as a contributing factor to speed.
  Authors: St-Aubin, Paul; Saunier, Nicolas; Miranda-Moreno, Luis Fernando; Ismail, Karim
  Authors: St-Aubin, Paul; Saunier, Nicolas; Miranda-Moreno, Luis Fernando; Ismail, Karim
  Year: 2013
  Document Type: Paper
  Subject: Design; Operations and Traffic Management; Safety and Human Factors
  Session: 626
  Paper Number: 13-5255
• Safety Effects of Converting Intersections to Roundabouts
  Abstract: This paper presents a before-after crash study of converting intersections to roundabouts in Denmark. General crash trends and regression-to-the-mean effects are accounted for by using correction factors estimated on the basis of 32 general comparison groups in this non-experimental observational study. 332 converted sites, 57 fatalities, 1,271 other injuries and 2,497 crashes are included in the study. Conversions have resulted in decreases in the numbers of crashes and injuries of 27% and 60% respectively. Crashes become less severe e.g. fatalities decreased by 87%, whereas property-damage-only (PDO) crashes only decreased by 16%.Safety effects vary between sites. The safety effect becomes better as the speed limit on the roundabout arms becomes higher. As the share of crashes at intersections, which are left-turn and angle crashes, becomes higher the safety effect becomes better. As the share of crashes at intersections, which are bicycle crashes, becomes lower the safety effect becomes better. Central islands more than two meters high produce better safety effects compared to lower central islands. Triangle or trumpet splitter islands produce better effects than no or parallel splitter islands. The numbers of bicycle crashes and injured cyclists have increased by 65% and 40% respectively due to the conversions. Cycle lanes next to the circulating lane have produced the worst safety effects for cyclists, whereas cycle paths without priority to cyclists resulted in the best effects. Colored cycle lanes and blue cycle crossings have produced worse safety effects for cyclists than comparable bicycle facilities without color.
  Authors: Jensen, Søren Underlien
  Authors: Jensen, Søren Underlien
  Year: 2013
  Document Type: Paper
  Subject: Design; Operations and Traffic Management; Safety and Human Factors
  Session: 626
  Paper Number: 13-1319
  Practice-Ready: Yes
• Effect of Signs and Striping on Roundabout Safety: Observational Before-and-After Study
  Abstract: This paper presents the study of the impact on driving behavior changes made to striping and signing at a two-lane roundabout located Richfield, Minnesota. After its completion, this roundabout exhibited an abnormal amount of crashes. In response to this, local engineers experimented with changes in the roundabout’s signs and striping, as roundabout design regulations are relatively lax and non-specific in contrast to ones for standard signalized intersections. An observational study was conducted that reduced 156 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 report 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 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 reduction of 55% in per capita occurrences of improper turns, and a 59% per capita reduction of drivers choosing the incorrect lane.
  Authors: Richfield, Veronica; Hourdos, John
  Authors: Richfield, Veronica; Hourdos, John
  Year: 2013
  Document Type: Paper
  Subject: Design; Operations and Traffic Management; Safety and Human Factors
  Session: 626
  Paper Number: 13-4568
  Practice-Ready: Yes
• Safety Effects of Converting Intersections to Roundabouts
  Authors: Jensen, Søren
  Authors: Jensen, Søren
  Year: 2013
  Document Type: Presentation
  Subject: Design; Operations and Traffic Management; Safety and Human Factors
  Session: 626
  Paper Number: 13-1319
• Emission Estimation at Multilane Roundabouts: Effect of Movement and Approach Lane
  Authors: Salamati, Katy
  Authors: Salamati, Katy
  Year: 2013
  Document Type: Presentation
  Subject: Design; Operations and Traffic Management; Safety and Human Factors
  Session: 626
  Paper Number: 13-0420
• Emission Estimation at Multilane Roundabouts: Effect of Movement and Approach Lane
  Authors: Bandeira, Jorge
  Authors: Bandeira, Jorge
  Year: 2013
  Document Type: Presentation
  Subject: Design; Operations and Traffic Management; Safety and Human Factors
  Session: 626
  Paper Number: 13-0420
• Effect of Signs and Striping on Roundabout Safety: Observational Before-and-After Study
  Authors: Hourdos, John
  Authors: Hourdos, John
  Year: 2013
  Document Type: Presentation
  Subject: Design; Operations and Traffic Management; Safety and Human Factors
  Session: 626
  Paper Number: 13-4568
• Detailed Driver Behavior Analysis and Trajectory Interpretation at Roundabouts Using Computer Vision Data
  Authors: St-Aubin, Paul
  Authors: St-Aubin, Paul
  Year: 2013
  Document Type: Presentation
  Subject: Design; Operations and Traffic Management; Safety and Human Factors
  Session: 626
  Paper Number: 13-5255