Presentation on theme: "Quang Le June 25, 2012 PERFORMANCE EVOLUTION OF THE DIVERGING DIAMOND INTERCHANGE Cal Poly Pomona."— Presentation transcript:
Quang Le June 25, 2012 PERFORMANCE EVOLUTION OF THE DIVERGING DIAMOND INTERCHANGE Cal Poly Pomona
Project Objective DDI Background Project Methodology Results Conclusions Further Research Questions OVERVIEW
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)
DDI OVERVIEW 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 1 ST DDI in Versailles, France (1970)
DDI IN THE UNITED STATES 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, DDI at MO-13 and I-44
ADVANTAGES 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.
CONFLICT POINTS IN A DDI TypeDiamondSPUIDDI Diverging1088 Merging1088 Crossing1082 Total302418
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). ADVANTAGES
DISADVANTAGES 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.
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
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.
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.
LocationSpacing (ft) Utah 1Main and I East and I Timpanogos Highway and I Highway 201 and Bangerter Rd.800 Tennessee 5US 129 and Bessemer St.650 Kentucky 6Harrodsburg Road and New Circle Road700 Missouri 7I435 and Front Street450 8US 65 and Missouri I44 and MO I270 and Dorsett Ave500 11Mo 60 and National Ave700 CURRENT DDI SPACING Avg~680ft
DDI SPACING SCENARIOS L=550 ft L=1,100 ft L=1,650 ft L=275 ft
Design and Operational Performance of a Double Crossover Intersection and Diverging Diamond Interchange” by Joe Bared 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 DATA DESCRIPTION
Northbound Off Ramp (vph) Southbound Off Ramp (vph) Eastbound (vph)Westbound (vph)Total Flow Traffic ScenarioLTRLTRLTRLTR(vph) High High Medium Low TRAFFIC VOLUMES
MICROSCOPIC SIMULATIONS 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
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
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
Traffic Scenario Model Delay Base Delay Low Base Delay Base Delay High % Error Low % Error% Error High 550 Low Median High High COMPARISON OF BASE MODEL (L=550 FT) WITH BARED PAPER
MODEL PARAMETERS Signal Timing Driver Behavior Settings Route Assignments Routing Decisions Areas of Reduced Speed Priority Rules Travel Time Locations Queue Counter Locations
LOCATION OF TRAFFIC SIGNALS 8 Total Signals and 6 phases were used
Phase 2=Phase 5 Phase 3=Phase 6 Signal Timing Diagram from Bared Study
Model from the Bared Study Yell=4 sec All Red =1 sec INITIAL SIGNAL TIMING PARAMETERS
UPGRADED SIGNAL TIMING PARAMETERS FOR L=1100 FEET SCENARIOS 18 second difference between signals
UPGRADED SIGNAL TIMING PARAMETERS FOR L=1650 FEET SCENARIOS 28 second difference between signals
Scenario Total Vehicles (Initial) 275Low Med High High Low Med High High Low Med High High Low Med High High25382 MODEL THROUGHPUT
DELAY RESULTS (BARED TIMING) Traffic Scenario Delay (sec/veh)) Stop Time (sec/veh) # Stops %Diff Delay %Diff Stop Time % Diff #Stops 275Low Med High High Low Med High High Low Med High High Low Med High High
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 DELAY RESULTS (BARED TIMING)
DELAY RESULTS (IMPROVED SIGNAL TIMING) Traffic Scenario Delay (sec/veh) Stop Time (sec/veh) # Stops %Diff Delay %Diff Stop Time % Diff #Stops 275Low Med High High Low Med High High Low Med High High Low Med High High
Updated signal timing shows a greater delay savings overall Improved overall performance, Same behavior where percent differences are higher for lower cross over spacing DELAY RESULTS (IMPROVED SIGNAL TIMING)
DIFFERENCE IN DELAY BETWEEN TWO SIGNAL TIMING PARAMETERS Traffic Scenario Delay (sec/veh) Stop Time (sec/veh)# Stops% Delay Savings 1100Low Med High High Low Med High High Greater delay savings shown for lower crossover spacing.
HCM DELAY FOR SIGNALIZED INTERSECTIONS LOSDelay (seconds) A0-10 B10-20 C20-35 D35-55 E55-80 F>80 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.
Movement Delay (HCM) Left from Corridor Avg.Left from Fwy Avg. Traffic ScenarioDelayLOSDelayLOS 275Low20.3C29.6C 275Med23.3C34.95C 275High133.9C65E 275High238.75D101.9F 550Low23.7C24.25C 550Med29.8C28.6C 550High151.8D34.75C 550High262.9E45.9D 1100Low21.1C21.5C 1100Med23.55C24.2C 1100High134.6C41.3D 1100High243.55D47.2D 1650Low17.9B24.7C 1650Med22.2C28.8C 1650High137.25D30C 1650High246.55D32.85C
DELAY VS. TRAFFIC VOLUME (BARED SIGNAL TIMING)
DELAY VS crossover DISTANCES (BARED SIGNAL TIMING)
DELAY VS. TRAFFIC VOLUME (MPROVED SIGNAL TIMING)
DELAY VS crossover DISTANCES (IMPROVED SIGNAL TIMING)
DELAY SUMMARY 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.
Traffic ScenarioAverage Speed (MPH) % Speed Diff. 275Low Med High High Low Med High High Low Med High High Low Med High High AVERAGE SPEED (BARED SIGNAL TIMING) Similar behavior as delay analysis.
ScenarioAverage Speed (MPH)% Speed Diff. 1100Low Med High High Low Med High High AVERAGE SPEED (IMPROVED SIGNAL TIMING) Overall higher average speeds are found.
Traffic Scenario Speed Difference (mph)% Difference 1100Low Med High High Low Med High High DIFFERENCES OF SPEED IN TWO TIMINGS
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.
SIMULATION OF MODEL AT L=275 FEET AND VOLUME=HIGH2
PROJECT SUMMARY DDI exhibits better performance in average speed, delay, and stop time in large crossover spacing DDI exhibits better performance in average speed, delay, and stop time under lower traffic volumes No significant advantages at lower traffic volumes Performance decreases as a faster rate as volume is increased at lower crossover spacing Optimizing the signal timing on the main corridor serves to significantly increase network performance Recommended spacing not be less than ~550ft DDI begins to show excessive delays
FUTURE RESEARCH More specific traffic patterns that focus on special cases where individual travel movements govern the system. Compare individual approaches and traffic movements, rather than the performance of the entire network. The task of updated the signal timing was limited in this study as to maintain signal timing as a constant in throughout the sixteen models. Research may be performed to compare the results of a 4-lane DDI with a 6-lane DDI. Pedestrian performance. They were omitted in this study as adding pedestrians to the system will have no impact to the vehicular traffic as long as the signal timing parameters for the pedestrians coincides with that of the vehicles. Further analysis on LOS requirements for DDI.