Detectors and Timing: Experiments and Results

1
Detectors and TimingExperiments and Results

• 19 October 2004

2
Book outline

• Part 1. Basic Concepts
• Overview
• Traffic operations and control on an intersection
  approach
• Traffic operations and control at an intersection
• Part 2. Advanced Concepts
• Intersection approach concepts
• Detection and timing parameters
• Vehicle clearance period
• Pedestrian phasing
• Other detection concepts

• Intersection concepts
• Rings and phase sequencing
• Left turn phasing
• Maximum green time/cycle length
• Preemption
• Other controller functions
• Part 3. Applications
• Signal timing design issues for an intersection
  approach
• Signal timing design issues for an intersection
• Field problem 1 Sixth Street and Deakin Street
• Field problem 2 Rural intersection with high
  speed approaches
• Other field problems

3
Assume side street operation

• What are the issues to be considered when
  locating detectors?
• Location
• Number
• Type (mode)
• What timing parameters must be considered at the
  same time?
• Minimum green
• Passage time (gap time)

4
6x6 loop Presence and pulse modes
6x20 loop Presence mode
6x6 loop Presence mode
5
Vehicle headways from beginning of green
6
Equivalent (instantaneous) flow rate at beginning
of green
7
(No Transcript)
8
Detector
9
Timer reset
Timer expires
Timers
Timer timing
10
Signal display
11
Flow rate
12
Direction of vehicle travel
13
Front of vehicle trajectory
Back of vehicle trajectory
14
Cases 04-06
Cases 01-03
15
(No Transcript)
16
(No Transcript)
17
(No Transcript)
18
(No Transcript)
19
(No Transcript)
20
(No Transcript)
21
How to Evaluate?

• Proportion of vehicles served?
• Unused green time?
• Other measures?

22

• Upstream detector is more efficient than stop bar
  detector.
• Based on unused green time.
• Lack of stop bar detector may trap a vehicle
  (i.e., it is not detected) if queue doesnt
  extend to detector at beginning of green.
• Or minimum green time is not sufficient.

23

24

• For this detector configuration, minimum green
  time must be sufficient to serve all vehicles in
  standing queue between detector and stop bar at
  the beginning of green
• Compare cases 2 and 2

25
Cases 07-09 (pulse mode)
26
(No Transcript)
27

• Pulse mode is not effective for upstream
  detector.
• Green terminates too early all vehicles in
  standing queue are not served.

28
Cases 10-12
29
(No Transcript)
30

• Long loop with presence mode is not efficient
  with normal values of minimum green time and
  passage time.
• The long loop duplicates the function of these
  two timing parameters.

31
Cases 13-15 (zero gap time and zero passage time
32
(No Transcript)
33

• Long loop with presence mode is efficient if
  minimum green time and passage time are set to
  zero.
• Equally efficient for queue of seven vehicles and
  longer.

34

• Long loop with presence mode is efficient if
  minimum green time and passage time are set to
  zero.
• Equally efficient as other alternatives for queue
  of four vehicles.

35

• Long loop with presence mode is efficient if
  minimum green time and passage time are set to
  zero.
• Most efficient of alternatives considered for
  short queue (1 vehicle).

36
(No Transcript)
37
(No Transcript)
38
(No Transcript)
39
(No Transcript)
40
(No Transcript)
41
(No Transcript)
42
(No Transcript)
43
(No Transcript)
44
(No Transcript)
45
(No Transcript)
46
(No Transcript)
47
(No Transcript)
48
(No Transcript)
49
(No Transcript)
50
(No Transcript)
51
(No Transcript)
52
Principles

• The green interval should terminate when the
  standing queue clears.
• Design decisions for detector location, detector
  mode, passage time, and minimum green time must
  be made concurrently.
• Short loop, presence mode, non-zero values for
  passage time and minimum green time.
• Long loop, presence mode, zero values for passage
  time and minimum green time.
• The minimum green time must be long enough to
  serve all of the vehicles that are queued between
  the detector and the stop bar.
• The detector should be located far enough back
  from the stop bar so that vehicles that pass over
  the detector are moving such that headways in the
  queue are equal to the saturation headway.
• The time for a vehicle to travel the distance
  between the detector and the stop bar should be
  equal to the passage time.

53
(No Transcript)
54

• Visual Basic for Applications toolbar
• VB editor
• Controls toolbox
• Design mode
• Script editor

55
1. Insert Module 2. Insert Procedure (either
Sub or Function)
56
(No Transcript)
57
(No Transcript)
58
(No Transcript)
59
(No Transcript)