Traffic Signal Warrants and Timing Relationships
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Signal Warrants
More Terms…
Basic Terminology
(2/2)
Lost time (l
i
)
Time lost due to starting and stopping
Total lost time (L)
Saturation flow
Flow at continuous movement assuming always
green
All-red interval (AR)
Time when all signals display red
More Terminology
Display Green (G
i
)
Time phase diplays green indication
Effective green (g
i
)
Time allocated to moving vehicles at saturation flow
Total effective green (g
T
)
Green ratio (g/C)
Timing Relationships
τ
Relationships
g
i
= G
i
- l
i
+
τ
i
τ
i
= Y
i
+ AR
i
g
T
= C - L
Flow Terminology
Discharge headway
Time headway for vehicles departing
Saturation flow (1,900 pcphgpl under ideal
conditions)
Greenshields’ Model
Change/Clearance Interval
Change/Clearance Interval
Minimum time between the green
indications of two phases
Yellow + All-red
Provide driver with enough time to safely
clear the intersection
Must be at least 3 seconds
Dilemma Zone
?
For no DZ Distance to stop = Distance to clear
Dilemma Zone - Time to Clear
?
X
o
W
L
Time to clear = (X
o
+ W + L) / U
o
=
τ
min
Dilemma Zone - Time to Stop
?
Distance to stop = X
c
= U
o
t
r
+ U
o
2
/ (2a+64.4G)
X
c
Dilemma Zone Elimination
Set Xc = Xo to eliminate dilemma zone
Rearrange and solve for
τ
min
Change/Clearance Interval
τ
min
= t
r
+ [
u
0
/(2a+64.4G)] + [(W+L)/u
0
]
W is road width to be cleared (ft or m)
L is vehicle length (ft or m)
u
0
is approach speed of vehicles (fps or m/s)
t
r
is driver’s reaction time (sec) (1.0 sec)
a is deceleration rate (fps
2
or m/s
2
) (10.0 ft/s
2
)
G is percent grade divided by 100
Change/Clearance Interval
τ
min
= t
r
+ [
u
0
/(2a+64.4G)] + [(W+L)/u
0
]
Yellow Time
All Red
Phase Plan
Protected or Permitted Left Turns?
Cross Product Left and Opposing Throughs
1 Lane; > 50,000
2 Lanes; >90,000
3 Lanes; >110,000
Explore the world of traffic signal warrants, basic terminology, and timing relationships with detailed visuals and explanations. Learn about lost time, green indications, effective green time, and flow terminology. Discover concepts like the Change/Clearance Interval and the Dilemma Zone in traffic management. Enhance your knowledge of traffic signal operations and principles through this informative presentation.
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Presentation Transcript
Signal Warrants http://mutcd.fhwa.dot.gov/htm/2009r1r2 /part4/part4c.htm Slide 2
Basic Terminology (2/2) Lost time (li) Time lost due to starting and stopping Total lost time (L) Saturation flow Flow at continuous movement assuming always green All-red interval (AR) Time when all signals display red Slide 4
More Terminology Display Green (Gi) Time phase diplays green indication Effective green (gi) Time allocated to moving vehicles at saturation flow Total effective green (gT) Green ratio (g/C) Slide 5
Timing Relationships Effective green Lost time Lost time Red Green Slide 6
Relationships gi = Gi - li + i i = Yi + ARi gT = C - L Slide 7
Flow Terminology Discharge headway Time headway for vehicles departing Saturation flow (1,900 pcphgpl under ideal conditions) Slide 8
Greenshields Model 4 3 Headway (sec) 2 1 0 1 2 3 4 5 6 7 8 Vehicle Number Slide 9
Change/Clearance Interval Minimum time between the green indications of two phases Yellow + All-red Provide driver with enough time to safely clear the intersection Must be at least 3 seconds Slide 11
Dilemma Zone Stop ? Clear For no DZ Distance to stop = Distance to clear Slide 12
Dilemma Zone - Time to Clear Stop ? Xo W L Time to clear = (Xo + W + L) / Uo = min Slide 13
Dilemma Zone - Time to Stop Xc ? Clear Distance to stop = Xc = Uotr + Uo2 / (2a+64.4G) Slide 14
Dilemma Zone Elimination Set Xc = Xo to eliminate dilemma zone Rearrange and solve for min Slide 15
Change/Clearance Interval min = tr + [u0 /(2a+64.4G)] + [(W+L)/u0] W is road width to be cleared (ft or m) L is vehicle length (ft or m) u0 is approach speed of vehicles (fps or m/s) tr is driver s reaction time (sec) (1.0 sec) a is deceleration rate (fps2 or m/s2) (10.0 ft/s2) G is percent grade divided by 100 Slide 16
Change/Clearance Interval min = tr + [u0 /(2a+64.4G)] + [(W+L)/u0] All Red Yellow Time Slide 17
