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Calcimator

Traffic Signal Timing Calculator

Calculate signal green time, effective green, volume-to-capacity ratio, and average delay per vehicle for signalized intersections.

Inputs

veh/hr
veh/hr/lane

HCM 6th Ed: base s₀=1,900 pc/h/ln; adjusted for width, turns, heavy vehicles; typical 1,700–1,900 vph

sec
sec
sec

MUTCD/HCM: urban 60–90 sec; major arterials 90–120 sec; Webster optimum typical 70–100 sec

Results

Green Time per Phase

39 sec

Volume/Capacity (v/c)

0.98

Effective Green41 sec
Delay per Vehicle24 sec
Approach Capacity820 veh/hr
Total Lost Time12 sec
How to Use This Calculator
  1. Enter approach volumes, saturation flow rates, and lost time per phase.
  2. Set number of phases and peak hour factor.
  3. Review cycle length, green time per phase, and level of service (v/c ratio).
  4. Target v/c ratios below 0.90 for acceptable intersection operation.

How the result changes with Number of Phases

Number of PhasesGreen Time per PhaseVolume/Capacity (v/c)
2.628.6 sec1.31
4.116 sec2.23
5.99.3 sec3.55
7.46.2 sec4.9

What each input means

Approach Volume
Traffic volume on the approach being analyzed, in vehicles per hour.
Saturation Flow Rate
Maximum flow rate through the intersection during green per HCM 6th Edition (TRB). Ideal base saturation flow: 1,900 vph/lane; typical default 1,800 vph/lane adjusted for lane width, turns, and grade.
Yellow Time
Duration of yellow (amber) signal phase. Typically 3-5 seconds based on approach speed.
All-Red Interval
Time when all signals are red for clearance. Typically 1-3 seconds depending on intersection width.
Number of Phases
Number of signal phases per cycle. Simple intersection = 2; with left turn phases = 4+.
Cycle Length
Total time for one complete signal cycle per MUTCD and HCM 6th Edition. Optimal cycle minimizes total delay: urban arterials 60–90 sec; high-volume intersections 90–120 sec; Webster's optimum formula: Co = (1.5L + 5)/(1 - Y).

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Approach Volume = 800, Saturation Flow Rate = 1800, Yellow Time = 4, All-Red Interval = 2 = 6 input(s) provided
  2. Calculate Green Time per Phase
    Green Time per Phase
    39 = 39
  3. Calculate Volume/Capacity
    Volume/Capacity
    0.976 = 0.976
  4. Calculate Effective Green
    Effective Green
    41 = 41
  5. Calculate Delay per Vehicle
    Delay per Vehicle
    24 = 24

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