PERFORMANCE EVOLUTION OF THE DIVERGING DIAMOND INTERCHANGE

1. PERFORMANCE EVOLUTION OF THE DIVERGING DIAMOND INTERCHANGE Quang Le June 25, 2012 Cal Poly Pomona

2. overview • Project Objective • DDI Background • Project Methodology • Results • Conclusions • Further Research • Questions

3. Project Objectives • Determine the behavior of several performance measures, such as delay, stop time, average speed, and queue length as the spacing between the two crossovers is increased or decreased. • Compare several performance measures using different volumes scenarios under fixed distances • Run models under a different signal timing parameter (not part of original proposal)

4. The diverging diamond interchange (DDI), also known as the double crossover diamond (DCD) interchange, provides an alternative design solution to mitigate traffic congestion. Allows Crossover of traffic to left side of the road to reduce traffic conflicts DDI overview 1ST DDI in Versailles, France (1970)

5. Eleven (11) DDI can be found in the US Missouri (5), Utah (4), Tennessee (1), and Kentucky (1). The first DDI opened to traffic in the United States was the interchange connecting MO-13 with I-44 in Springfield, Missouri on June 21, 2009. Ddi in the united states DDI at MO-13 and I-44

6. Vehicle Safety Ex: The average number of reported traffic accidents before the DDI was fifty-three. Reduced to twenty-five in the one year after the DDI was constructed and open to the public (Missouri DOT). Pedestrian safety is increased as accidents resulting from turning movements are eliminated. The DDI has been shown to increase the capacity of the system. advantages

7. CONFLICT POINTS IN A DDI

8. Advantages • Reduction of total delay in the system. The DDI reduces the number of signals that are required in the system • The delay is decreased because the two interchanges are reduced to a two phase signal. This creates shorter cycle lengths and allows for the loss time to be saved from having fewer signal phases, which can be transferred to the green time. • Construction costs in a DDI have proven to be more economical than other conversions (Missouri DOT 2010).

9. Lack of Sample Size (first one built in 2009) Traffic restrictions at the off-ramps to either a left or right turn Public Perception: General public, engineers, political The DDI is designed to work with heavy left turning volumes. Under free-flowing traffic conditions along the corridor, this design will become redundant, and actually increase the delay of the intersection with conflicts between opposing direction of travel. Limited resources to reference when designing a new diverging diamond interchange. As a result, design criteria, such as signal timing and signal warrants, level of service criteria have not been generalized for the DDI. disadvantages

10. PROJECT METHODOLOGY • Creation of initial model at L=550’ crossover spacing under low traffic volumes using same traffic parameters (same signal timing). • Calibrate model within 10% accuracy of the Bared paper. • Create model and simulate results for the remaining traffic volumes at L=550’ to obtain results as in the paper. • Increase crossover spacing to L=1,100ft, 1,650ft, and 275ft to develop further models. • Evaluate data output from VISSIM. • Alter signal timing to obtain better performance results in each DDI and compare the results

11. INITIAL HYPOTHESES • Currently, it can be deduced that larger interchange spacing between the on ramps and off ramps will be able to accommodate a larger traffic volumes in the system, resulting in fewer overall delays. • Developed during the literature review stage.

12. DIVERGING DIAMOND INTERCHANGE • Three lanes of traffic in each direction of the cross streets. • The right most lane merges into the freeway onramps, and the interchange becomes a two lane DDI between the two crossovers. • The roadway then remains two lanes leaving the DDI on the cross streets. • The northbound and southbound both have one lane for right turn traffic and two lanes for left turn traffic.

13. Geometrics

14. Current DDI Spacing Avg~680ft

15. DDI SPACING SCENARIOS L=550 ft L=1,650 ft L=275 ft L=1,100 ft

16. Data description • Data taken from: “Design and Operational Performance of a Double Crossover Intersection and Diverging Diamond Interchange” by Joe Bared • Read only file from Bared with Input values

17. Traffic volumes

18. TRAFFIC VOLUMES

19. VISSIM is a microscopic, time step and behavior-based simulation model Each entity is simulated individually Macro: averages simulation Microscopic simulation is a safer, less expensive, and faster than field implementation and testing. Provides the ability to control factors not easily measured in the field. Cannot obtain field data for this project VISSIM Developed by PTV from Germany Difficulties modeling DDI with other software, such as SYNCHRO MICROSCOPIC SIMULATIONS

20. MODEL CONSTRAINTS • Existing Geometry / Lane configuration • Traffic parameters from Bared Study were used to obtain similar results • Adjacent Intersections/ramps (focus on DDI network) • No Pedestrian traffic were modeled • One signal timing from Bared Study was used

21. Model Calibration/Verification • Model calibration is defined as the process by which the individual components of the simulation model are adjusted or fine tuned so the model will accurately represent field measured or observed traffic conditions. • Usually performed with real life data, in this case, data generated from the Bared Study. • Goal: 10% of the MOEs as determined in the Bared Study. • Delay • Stop Times

22. Comparison of Base Model (L=550 ft) with Bared Paper

23. Signal Timing Driver Behavior Settings Route Assignments Routing Decisions Areas of Reduced Speed Priority Rules Travel Time Locations Queue Counter Locations Model parameters

24. 8 Total Signals and 6 phases were used. Location of traffic signals 5 1 3 4 1 6 2 4

25. Signal Timing Diagram from Bared Study • Phase 2=Phase 5 • Phase 3=Phase 6

26. Initial Signal Timing Parameters • Model from the Bared Study • Yell=4 sec • All Red =1 sec

27. 18 second difference between signals Upgraded Signal Timing Parameters for L=1100 feet scenarios

28. 28 second difference between signals Upgraded Signal Timing Parameters for L=1650 feet scenarios

29. Results

30. Model throughput

31. Delay results (bared timing)

32. Delay results (bared timing) • Consistent trend that delay increases with increasing traffic volumes and is reduced as crossover spacing is increased • Same trend for number of stops and stop times • A greater percent delay difference is found in lower crossover spacing and higher volume scenarios • Shows that the DDI is more sensitive under these conditions

33. Delay Results (improved Signal Timing)

34. Delay Results (improved Signal Timing) • Updated signal timing shows a greater delay savings overall • Improved overall performance, • Same behavior where percent differences are higher for lower cross over spacing

35. DIFFERENCE IN DELAY BETWEEN TWO SIGNAL TIMING PARAMETERS • Greater delay savings shown for lower crossover spacing.

36. HCM DELAY FOR SIGNALIZED INTERSECTIONS • Applying values to DDI are over exaggerated, but gives a starting point for a comparative analysis. • HCM does not have dedicated table for DDI, used for relative comparison purposes only.

37. Movement Delay (HCM)

38. Delay vs. Traffic Volume (bared signal timing)

39. Delay vs. Traffic Volume (bared signal timing)

40. DELAY VS crossover DISTANCES (BARED SIGNAL TIMING)

41. DELAY VS crossover DISTANCES (BARED SIGNAL TIMING)

42. DELAY VS. TRAFFIC VOLUME (MPROVED SIGNAL TIMING)

43. DELAY VS crossover DISTANCES (IMPROVED SIGNAL TIMING)

44. DELAY VS crossover DISTANCES (IMPROVED SIGNAL TIMING)

45. Delays consistently increase as volumes increase in each scenario being modeled. Delays consistently increase as crossover spacing is decreased. Greater percent difference in delays and stop times as crossover is decreased and volumes is increased Sensitivity of the models. Using an updated signal timing increases the delay savings. Isolating the delays for left turning movements allows us to examine performance of key turning movements. Same results were found for stop time and number of stops DDI shows poor performance in the L=275 scenario, best as cross over spacing is increased. Delay summary

46. Average Speed (bared Signal Timing) • Similar behavior as delay analysis.

47. Average Speed (improved signal timing) • Overall higher average speeds are found.

48. Differences of speed in two Timings

49. Average Speed Summary • Average speed consistently decreases as volumes are increased. • Average speed consistently increases as crossover spacing is increased. • Similar results as delay concerning increased sensitivity at higher volumes and lower crossover spacing.

50. Simulation of Model at L=275 feet and Volume=High2