Transcript Introduction to Traffic Signal Design

Detector Operation and Timing
Bill Kloos
Signals & St Lighting Mgr.
City of Portland
July 28, 2003
Best Practices for Signal Operations
A typical day in Portland!
Really!!!
Traditional Approach
• Why have the
presence detection
and still have the
sign?
• How does this relate
to detection in the
street?
• Or, the real question
is:
• What’s Peter’s thing
about the toilet???
Talk outline for today
• What type of controllers & software do we
use? What are the basic parameters?
• Differences in through movement
operation vs. left turns and side streets
• Example of how our left turn design works
• Various issues and questions
Detection Timing - City of Portland
• Use Type 170 controllers
• Wapiti IKS actuated controller software
• Primarily use ILD (round loops)
• Basic detection timing functions used:
– Min green
– Passage
– Volume density (TBR, TTR, Min gap,added/actuation)
• Try not to violate KISS principle
Typical data sheet
Functions
Wapiti IKS main actuated features
Veh Recall
Ped Recall
Red Lock
Yellow Lock
Permit
Ped Phases
Lead Phases
Double Entry
Seq Timing
Start Up Grn
Overlap A
Overlap B
Overlap C
Overlap D
Exclusive
Sim Gap
Phase
12345678
x
x
x
x
xxxxxxxx
x x x x
x x x x
x
x
x
x
Phases
Max I
Max II/HFDW
Walk
FDW
Max Initial
Min
TBR
TTR
Observe Gap
Passage
Min Gap
Add/Act
Yellow
Red Clear
Red Revert
Walk II
1
0
0
0
0
0
0
0
0
--0
0
0
0
0
0
0
2
0
0
0
0
0
0
0
0
--0
0
0
0
0
0
0
3
0
0
0
0
0
0
0
0
--0
0
0
0
0
0
0
4
0
0
0
0
0
0
0
0
--0
0
0
0
0
0
0
5
20
30
0
0
3
3
0
0
--0.5
0.5
0
3
0
0
0
6
0
0
0
0
0
0
0
0
--0
0
0
0
0
0
0
7
0
0
0
0
0
0
0
0
--0
0
0
0
0
0
0
8
0
0
0
0
0
0
0
0
--0
0
0
0
0
0
0
Detection Timing - City of Portland (cont)
• Multiple input channels per phase
– Allows carryover/delay programming within CPU
• Can have 3 sets of timing parameters (time
transfer)
• Have separate table for entering carryover and
delay by channel
• Can do various “tricks” with Command Box
Advance detection vs stop bar
• Use method demonstrated by Dave Hatch
for advance detection
• For side streets and left turns, use twodouble loops from stop bar and one single
detector at 100’ from stop bar.
• Most side streets set in “non-locking”
operation
Left Turn
Example SW Barbur &
Hamilton
Timing
36’
100’
•Min = 6 sec (typically 3 sec)
•Ext = 0.5 sec
•Yellow = 3.0 sec
Left Turn Example SW Barbur &
Hamilton
•Carryover back
loop = 2.1 sec
Opposing traffic
indication
LT lane
How it should work
Single vehicle issue
min overrides
gap time
Max out problems
LT signal now yellow
LT signal now red
Issues and questions
• Advance detection based on dilemma zone
protection – What happens when the phase maxes out?
– How do we handle the boundary between free flow
operation and congestion?
Issues and questions
• When should we display the yellow to the
approaching motorist?
– Portland method displays the yellow when motorist is
at stop bar
– Some research suggests that most motorists will not
stop when yellow is displayed less than 2 seconds in
advance of stop bar
– For efficiency, shouldn’t we display the yellow that
much sooner?
– Note on this question - somebody else try first
Issues and questions
• Is detection technology really that much better
now?
– Concerns about video during various weather and
lighting conditions
– How reliable is reliable enough?
– Are we straying away from the KISS principle?
Finally Is there a silver bullet
detection solution for our
transportation problems?
No, but maybe by using
old techniques and new
technology we can come
up with some silver
buckshot that will make
things better!
And if you have questions
Ask
Willie!