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Calcimator

Wildlife Passage Design Calculator

Calculate underpass or overpass dimensions for target wildlife crossing species, including openness ratio and cost estimation.

Inputs

meters
vehicles/day

Results

Recommended Width

6 m

≈ 4 adult heights

Recommended Height

4.5 m

≈ 3 adult heights

Openness Ratio1.93
Openness AdequacyExcellent
Total Estimated Cost$249,000.00
Construction Cost$216,000.00
Guide Fencing Cost$18,000.00
Expected Collision Reduction39%
Annual Collision Savings$6,240.00
Payback Period39.9 years
How to Use This Calculator
  1. Select target species size (small mammal, deer, bear, etc.) to set dimension requirements.
  2. Enter the road width and average daily traffic volume.
  3. Select passage type (culvert, overpass, underpass, etc.) and soil type.
  4. Review recommended width, height, and openness ratio.
  5. Verify openness adequacy rating meets wildlife passage design guidelines before finalizing construction plans.

What each input means

Target Species Size
1 = Small (reptiles, amphibians), 2 = Medium (fox, raccoon), 3 = Large (deer), 4 = Very Large (elk, bear, moose).
Road Width
Total road width including shoulders that the passage must span.
Average Daily Traffic
Average daily traffic count on the road.
Passage Type
1 = Culvert, 2 = Underpass, 3 = Overpass (land bridge), 4 = Bridge adaptation.
Soil Type
1 = Rock (higher excavation cost), 2 = Clay, 3 = Sand/Gravel.

What each result means

Openness Ratio
Cross-section area / length. Should be >0.6 for large mammals.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Target Species Size = 3, Road Width = 12, Average Daily Traffic = 10000, Passage Type = 2 = 5 input(s) provided
  2. Calculate Recommended Width
    Recommended Width
    6 = 6
  3. Calculate Recommended Height
    Recommended Height
    4.5 = 4.5
  4. Calculate Openness Ratio
    Openness Ratio
    1.93 = 1.93
  5. Calculate Openness Adequacy
    Excellent = Excellent

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