Traffic Signal Timing Diamond Operation. Innovation for better mobility

Transcription

1 Traffic Signal Timing Diamond Operation

2 Classic Diamond Interchange Page 2 2

3 What is a Diamond? Page 3 3

4 What is a Diamond? (Signal Terms) Two closely spaced signalized intersections of an arterial with a one way pair of frontage roads (Works more efficiently with one controller than two) Arterial Interior Frontage Road Page 4 4

5 Diamond Interchange Operation Phasing Options 4 Phase 3 Phase Separate Intersection Mode Page 5 5

6 Phasing Considerations Make it Efficient: run the heaviest movements together Three Phase Allows the main street phases (2+6) or (4+8) Four Phase Allows limited time for the Arterial and opposite side ramp Page 6 6

7 Phasing Considerations Lane Use Interchange Geometry Width of the Interchange (Internal Storage Capacity) Number of Lanes on The Approach Capacity Entering vs Capacity Inside Volume Distribution Origin Destination Page 7 7

8 Phasing Considerations Selection of Left Turn Treatment Hardware available Accident history Number of lanes Permissive should not be used with dual left turn lanes. Conflicting Vehicle Speeds Permissive should not be used with approach speeds over 40. Number of Lanes to Cross Permissive should not be used when crossing 3 or more lanes. Page 8 8

9 Classic Three Phase Arterial Interior Frontage Road Arterial Interior Clearance Frontage Roads Page 9 9

10 Three Phase Applications Most Effective: Wide Interchanges Provide adequate internal storage Rural Areas with Light Overall Traffic Fewer movements shorter cycle lengths Heavy Through Movements Will be ran simultaneously without having to cross each other Page 10 10

11 Classic Four Phase Right Arterial Right Frontage Left Arterial Left Frontage Page 11 11

12 Four Phase Applications Most Effective: Tightly Spaced Interchanges No adequate internal storage Urban Areas More movements longer cycle lengths Heavy Turning Movements Each exterior movement runs independently Page 12 12

13 Three Phase Examples Wide Intersection Spacing Rural Area (Light Traffic) Page 13 13

14 Three Phase Examples Wide Intersection Spacing Rural Area (Light Traffic) Page 14 14

15 Three Phase Examples Freeway not built yet (heavy through traffic) Page 15 15

16 Four Phase Examples Narrow Urban Diamonds Heavy Turning Traffic Page 16 16

17 Four Phase Examples Narrow Urban Diamonds Heavy Turning Traffic Page 17 17

18 Four Phase Examples Narrow Urban Diamonds Heavy Turning Traffic Page 18 18

19 Four Phase Examples Narrow Urban Diamonds Heavy Turning Traffic Page 19 19

20 Basic Three Phase Sequence Very efficient under light, even volume distribution. Problem: Does not handle uneven traffic volumes well. Page 20 20

21 Texas Three Phase Allows shorter, more efficient cycles Flexible Phasing in free and coordination Interior clearance after arterial phases Conditional Service allows backup to re-service interior with frontage road Conditional Service Intervals Page 21 21

22 Texas Diamond 3 Phase OL K=4+12 OLA= OLI OLL= OLB= OLN=8+16 Page 22 22

23 Basic Four Phase Sequence Attempts to provides progression for every entering vehicle. Problem: Tends to have long cycle lengths. Page 23 23

24 Texas Four Phase Adds two travel time (fixed time) phases into 4-phase cycle Increases efficiency Shortens Cycle Lengths Minimizes interior stops by providing internal clearances for every entering movement Travel Time Right Arterial Right Front. Rd Fixed Time Phase Left Arterial Left Front. Rd Travel Time Fixed Time Phase Page 24 24

25 Classic Four Phase Sequential Phasing Progresses every movement 25% 25% 25 s 25 s 25 s 25% 25 s 25% 100 Second Cycle Page 25 25

26 Texas Four Phase Same Splits 31 % 25 s 15 s 20% Shorter Cycle 31 % 25 s 15 s 10 s 25 s 31% 15 s 15 s 25 s 31% Wraps around 10 s 80 Second Cycle Page 26 26

27 Texas Diamond TTI 4 Phase Provides One Stop Operation Always keeps the interior clear Allows fully actuated operation Page 27 27

28 Texas Diamond Overlap Assignments OL K=4+12 OLA= OLI OLL= OLB= OLN=8+16 Page 28 28

29 Texas Diamond: 3 Phase - 4 Phase Both use the same load switch assignments Both use the same detector assignments Ring Structures are Different They have a common phase which is used when switching between 3 and 4 phase operation Page 29 29

30 Ring Structures Texas Three Phase Texas Four Phase Page 30 30

31 Diamond Detector Layout Page 31 31

32 Ramp Detector Placement T = Travel Time for Phase 2 D = Detector Setback = Distance traveled during T+2 Phase 8 D Example: T = 8 seconds Phase 8 approach speed = 40MPH D = (8+2) x (40x1.47) = 588 Travel Time Phase 2 Page 32 32

33 The Magic of a Diamond Interchange Controller There is none! Pre-programmed controller for standardization Uses standard controller features Same programming rules apply Minimum Green Maximum Green Extension Page 33 33

34 Modifying a Diamond Pre-Assigned detectors (1 18) are NOT programmable Detectors above #19 are programmable Overlaps are programmable Page 34 34

35 Customizing Diamond Phasing Overlaps Are Programmable Allow you to customize odd intersections Suggestion: Standard Diamonds Use Default Ring Structure Add/Alter Overlaps Where Needed Suggestion: Unique Applications Sequential Phasing All Overlaps Page 35 35

36 Problem Heavy Right Turn Driving the Ramp Time Page 36 36

37 Heavy Right Turn Driving the Ramp Time: How the movements work together Phase 4 and 5 Progressing the SB Movement Phase 12 and 6 Right to Left Travel Time Phase 1 and 6 WB green till gap termination NOTE: After first 8 seconds, no one flows EB Phase 1 and 8 NB Ramp - Right turn finally gets a green Page 37 37

38 Phasing: Diamond Mode with Additional Overlaps Frontage Road Right Turn Page 38 38

39 Phasing Modifications Texas Four Phase Available Phase Available Phase 6? 8 Page 39 39

40 Overlap Assignments with Right Turn Overlap OL K=4+12 OLA= OLC=6+7 OLI OLL= OLB= OLN=8+16 Phase 7 Page 40 40

41 Problem Two Way Ramp Needing Left Turn Protection Page 41 41

42 Phasing : Diamond Mode with Additional Overlaps Exterior Left for 2-Way Frontage Road Page 42 42

43 Phasing Modifications Texas Four Phase Available Phase Available Phase 6? 8 Page 43 43

44 Overlap Assignments with Right Turn Overlap OL K=4+12 OLA= OLC=6+7 OLI Phase 7 2 OLL= OLB= OLN=8+16 Page 44 44

45 Problem Closely Spaced Intersection to a Diamond OL K= OLA= OLI OLL= OLB= OLN=8+16 Page 45 45

46 Phase Sequence Diagram - Diamond Mode with Adjacent Intersection OL K=4+12 OLA= OLI OLL= OLB= OLN=8+16 Page 46 46

47 Overlap Assignments Diamond Mode with Adjacent Intersection 5 2 OL K= OLD= OLO=6 OLA= OLI OLC=2+8 2 OLL= OLB= OLP=4 OLN= Page 47 47

48 Split Diamond: Diamond Mode with modified Overlaps Page 48 48

49 Texas Four Phase Texas Three Phase Right Arterial Right Front. Rd Travel Time Fixed Time Phase Left Arterial Left Front. Rd Travel Time Fixed Time Phase Conditional Service Intervals Page 49 49

50 Modified Three Phase Diamond Advantages: Runs through movements together Provides progression for left turns Design the Ring Structure A D Ph 2 B Ph 4 D B Ph 5 Ph Assign the Overlaps A B C D Ph 4 Ph 8 A Ph 3 C Ph 8 A Ph 1 C Ph 6 B A Ph 2 B Ph 6 Page 50 50

51 Modified Three Phase: Overlap Assignments 4 OLA OLC 6 2 OLD OLB 8 Page 51 51

52 Diamond Operation with coordination Coordination rule changes for diamond controllers Dependent on ring structure Still a traffic signal controller Page 52 52

53 Three Phase Diamond Coordination Phases not serviced in the normal sequence Rules: 4=8 1+2=5+6 Cycle Length = or Coordinated phase in each ring, on the same side of the barrier (4+8, 2+6, 1+6, 2+5, 1+5) Page 53 53

54 Four Phase Diamond Coordination Service road time is a combination of two phases Rules: 5 must be shorter than 4 and 2 s min time 1 must be shorter than 8 and 6 s min time Cycle Length = Coordinated phase in each ring, on the same side of the barrier (2+5, 4+5, 1+6, 1+8) Page 54 54

55 Innovative Intersection Designs Based on intersection geometry Goals Reduces the number of phase intervals Reduces cycle length Options Diverging Diamond Displaced Left Turn Diamond Page 55 55

56 Diverging Diamond Page 56 56

57 Round Rock Diverging Diamond Field Observation: Made best use of existing bridges The original phase sequence created multiple stops for the left service roads that the city wanted to change Driver routes were not as anticipated Created weaving issue with downstream intersection Page 57 57

58 Displaced Left Turn Diamond Page 58 58

59 San Marcos Displaced Left Turn Diamond Field Observation: Took advantage of existing number of lanes under the bridge Internal storage not adequate for the 3 phase operation Single left turn lane was not adequate WB Multiple pedestrian crossing point affected phasing Page 59 59

60 Hybrid Diamond????? Page 60 60

61 Questions and Comments Page 61 61