Signal Warrants

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Signal Warrants
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Signal Warrants

• http//mutcd.fhwa.dot.gov/htm/2009r1r2/part4/part4
  c.htm

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More Terms
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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

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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)

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Timing Relationships
t
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Relationships

• gi Gi - li ti
• ti Yi ARi
• gT C - L

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Flow Terminology

• Discharge headway
• Time headway for vehicles departing
• Saturation flow (1,900 pcphgpl under ideal
  conditions)

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Greenshields Model
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Change/Clearance Interval
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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

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Dilemma Zone
?
For no DZ Distance to stop Distance to clear
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Dilemma Zone - Time to Clear
?
Xo
W
L
Time to clear (Xo W L) / Uo tmin
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Dilemma Zone - Time to Stop
Xc
?
Distance to stop Xc Uotr Uo2 / (2a64.4G)
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Dilemma Zone Elimination

• Set Xc Xo to eliminate dilemma zone
• Rearrange and solve for tmin

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Change/Clearance Interval

• tmin tr u0 /(2a64.4G) (WL)/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 drivers 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

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Change/Clearance Interval

• tmin tr u0 /(2a64.4G) (WL)/u0

All Red
Yellow Time
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Phase Plan

• Protected or Permitted Left Turns?
• Cross Product Left and Opposing Throughs
• 1 Lane gt 50,000
• 2 Lanes gt90,000
• 3 Lanes gt110,000