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Calcimator

Speed Hump Design Calculator

Design speed humps, speed tables, or speed cushions with recommended dimensions and spacing for target speed reduction on residential streets.

Inputs

mph
mph
ft
%

Results

Device Height

3 in

Total Length

12 ft

≈ 24 smartphones

Ramp Length6 ft
Flat Top Length0 ft
Device Width26 ft
Recommended Spacing350 ft
Speed Reduction10 mph
Expected Speed25 mph
Emergency CompatibilityOK
How to Use This Calculator
  1. Enter Device Type, Speed Hump (sinusoidal), and Speed Table (flat top).
  2. Set Speed Cushion (emergency-friendly), Target Speed, and Current 85th % Speed.
  3. Adjust Road Width, Downhill Grade as needed.
  4. Review Device Height (in) and Total Length (ft).
  5. Use Ramp Length (ft) and Flat Top Length (ft) to inform your decision.

How the result changes with Target Speed

Target SpeedDevice HeightTotal Length
174 in10 ft
223 in12 ft
282.5 in14 ft
332.5 in14 ft

What each input means

Device Type
Type of vertical traffic calming device. Cushions have wheel-track gaps for emergency vehicles.
Target Speed
Desired 85th percentile speed at the device location.
Current 85th % Speed
Existing 85th percentile speed measured on the street.
Road Width
Curb-to-curb pavement width.
Downhill Grade
Downhill grade at the hump location. Steeper grades reduce device effectiveness.
Emergency Route
Whether the street is a designated emergency vehicle route.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Device Type = 1, Target Speed = 25, Current 85th % Speed = 35, Road Width = 28 = 6 input(s) provided
  2. Calculate Device Height
    Device Height
    3 = 3
  3. Calculate Total Length
    Total Length
    12 = 12
  4. Calculate Ramp Length
    Ramp Length
    6 = 6
  5. Calculate Flat Top Length
    Flat Top Length
    0 = 0

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