James H. Dunlop NCDOT Congestion Management Section

1. James H. DunlopNCDOTCongestion Management Section Congestion Management Optionsto Improve Air Quality

2. Ideal Driving Conditions

3. Usual Driving Conditions

4. Intersections A place where two or more roads meet

5. Conventional Intersection Conflict Points

6. Intersection Congestion What is the traffic control device that leads to more confusion, congestion and air pollution than any other?

7. Intersection Congestion The Traffic Signal

8. SignalizedIntersections The Purpose of a Traffic Signal is to take the Right-of-Way assignment away from the main flow of traffic and assign it to lesser movements

10. Main Street Green Time Main Phase ~ 70% Green Main Phase ~ 50% Green Main Phase ~ 33% Green

11. Signalized Intersections Eight-Phase Signal

12. Intersections Does every intersection need every movement served at the same location?

13. Alternative Intersection Design Concepts • Separate conflicting movements • Reduce conflicts • Remove signals where possible • Limit phases at signalized intersections • Provide better signal coordination

14. Alternative Intersection Design Concepts • Roundabouts • Superstreets • Quadrant Lefts • Jughandles • Offset “T” Intersections • Continuous Flow Intersection

15. Circular Intersections 3 Types of Circular Intersections • Traffic Circle Columbus Circle – New York City Market Square - Fayetteville

16. Circular Intersections 3 Types of Circular Intersections • Traffic Circle • Traffic Calming Intersection

17. Circular Intersections 3 Types of Circular Intersections • Traffic Circle • Traffic Calming Intersection • Modern Roundabout Clemmons, Forsyth Co. NC State, Raleigh

18. Roundabout vs. Traffic CircleSize Traffic Circle - ~ 800’ Diameter Roundabout – ~ 180’ Diameter

19. Roundabout vs. Traffic CircleDeflection Traffic Circle – 90 degree entry Roundabout – 45-60 degree entry

20. Roundabout vs. Traffic CircleEntry Traffic Control Traffic Circle - Stop Roundabout - Yield

21. Why Roundabouts? • Safest Intersection • High Capacity / Low Delay • Good for All Modes of Traffic • Geometric Flexibility • Aesthetics

22. Roundabouts - Safety There are 32 conflict points at a conventional intersection. There are only 8 conflict points at a modern roundabout

23. Roundabouts - Safety Crash Reductions Following Installation of Roundabouts • In the United States – 2007 • Total Crashes 48% • Fatal/Injury Crashes in Rural Areas 78% • Fatal/Injury Crashes in Urban Areas60% In North Carolina from 1999-2006 • Conversion From Stop Sign Control 41% • Conversion From Signal Control 74% Sources: Insurance Institute For Highway Safetywww.highwaysafety.org NCHRP Report 572 onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_572.pdf NCDOT Safety Evaluation Groupwww.ncdot.org/doh/preconstruct/traffic/safety/Reports/completed.html

24. Roundabouts -Capacity and Operation • Peak Hour Traffic – Usually at least as efficient (same overall delay to drivers) as traffic signals or all-way stops • Off Peak Traffic – Usually much more efficient than traffic signals. • Multi-lane roundabouts can handle as much traffic as a busy signalized intersection

25. Roundabouts – Multi-Modal • Roundabouts provide a safer crossing for pedestrians

26. Roundabouts – Multi-Modal • Roundabouts provide safer travel for cyclists PHOTOGRAPHY SOURCE: Lee Rodegerdts

27. Roundabouts – Multi-Modal

28. Roundabouts – Multi-Modal • Buses do not have trouble negotiating the roundabout, and provide a good location for bus stops

29. Large Trucks PHOTOGRAPHY SOURCE: Lee Rodegerdts

30. Emergency Vehicles PHOTOGRAPHY SOURCE: Brian Walsh

31. Roundabouts – Geometric Flexibility

32. Roundabouts – Geometric Flexibility • Roundabouts can be designed as ovals and oblong shapes in order to achieve better movement separation and accommodate unique intersection geometry • Works well for offset T-type and multiple legged intersections • Could be an option for median divided facilities where controlling access is an issue

33. Roundabouts – Geometric Flexibility Corridor Operation

34. Landscaping

35. Landscaping Bloomington, IN

36. Landscaping Houten, the Netherlands

37. Roundabout Air Emissions At a roundabout replacing a signalised junction, CO emissions - 29% NOxemissions - 21% fuel consumption - 28% At a roundabout replacing yield regulated junctions, CO emissions + 4% NOxemissions + 6% fuel consumption + 3% “The results indicate that the large reductions in emissions and fuel consumption at one rebuilt signalised junction can “compensate for” the increase produced by several yield-regulated junctions rebuilt as roundabouts.” The effects of small roundabouts on emissions and fuel consumption: a case study AndrásVárhelyi, Department of Technology and Society, Lund University, Sweden 2001

38. Roundabout Air Emissions Better fuel efficiency and air quality Where roundabouts replace signals, idling decreases which reduces vehicle emissions and fuel consumption by 30 percent or more. http://www.dot.state.mn.us/roundabouts/ (Minnesota DOT)

39. NY State Study Roundabout vs. Signalized intersection

40. Intersection Costs • Average Roundabout construction costs about $400,000 • Maintenance is minimal (mostly mowing any additional landscaping is done by others) • Signalized intersection costs are about $100,000 • Signal maintenance costs are about $3,000-5,000 annually • Construction of turn lanes is about $75,000-$150,000

41. North Carolina Roundabouts Inventory as of August 2010

42. Single Lane Roundabouts Clemmons, Forsyth Co.

43. Single Lane Roundabouts NC State, Raleigh

44. Griffith Street and Davidson Gateway Drive Griffith Street andJetton Street Davidson, NC Multi Lane Roundabouts

45. Superstreets • Minor cross street traffic must turn right, but can then access a U-turn to proceed in the desired direction. • A type of intersection in which minor cross-street traffic is prohibited from going straight through or left at a divided highway intersection. *Other configurations possible based on site specific conditions.

47. Improved Safety Less Travel Time Economically Beneficial Environmentally Responsible Why Superstreets?

48. Why Superstreets? Improved Safety Reduced conflict points (especially crossing movements) leads to reduced crashes

49. Superstreet Conflict Points Total Conflict Points = 14 Improved Safety

50. Superstreet Benefits and Capacities(Research Project 2009-06) Safety impact by collision type for unsignalized superstreets, %