Haul Road Design
Running width, curve widening, superelevation and stopping distance for the biggest truck on the road. The stopping check is the one that matters: a loaded truck on a descent needs far more room than most people expect.
Step 1: The biggest truck on the road
Every dimension below is set by the largest vehicle using the road on a regular schedule, not the average one.
Step 2: The road
Lanes and the tightest bend on the segment you are designing.
Step 3: Braking
The published defaults are Kaufman and Ault's. Change them only with test data.
What you get
Every figure traces to a printed page in the working below.
- Running width, straight and through the bend
- Superelevation for the curve at your design speed
- Stopping distance, checked against the 61 m (200 ft) limit
- Sight distance you must hold to make that stop
- Total resistance for the climb out
| Step | Value | Where it comes from |
|---|
Road cross-section, to scale
Stopping distance
Road width multipliers
| Lanes | Factor × widest vehicle |
|---|---|
| 1 | 2.0 |
| 2 | 3.5 |
| 3 | 5.0 |
| 4 | 6.5 |
| Vehicle on a bend | 6 m (20 ft) | 45 m (150 ft) | 60 m (200 ft) |
|---|---|---|---|
| Rear-dump and unitized trucks | 125% | 118% | 110% |
| Articulated trucks | 155% | 135% | 115% |
SME Mining Reference Handbook, 2nd ed., pp. 323-324. The curve figures are a percentage of the straight-road width, by inside radius. Past 60 m (200 ft) the published table stops and no widening is applied here.
Superelevation rates by curve radius and speed
| Radius, m | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| 50 | 3.5% | 6.0% | 9.0% | ||||||
| 75 | 2.5% | 4.5% | 7.0% | 9.0% | |||||
| 100 | 2.0% | 3.5% | 5.0% | 7.5% | 9.0% | ||||
| 150 | 2.0% | 2.5% | 3.5% | 5.0% | 6.5% | 8.5% | |||
| 200 | 2.0% | 2.0% | 2.5% | 3.5% | 5.0% | 6.5% | 8.0% | ||
| 300 | 2.0% | 2.0% | 2.0% | 2.5% | 3.5% | 4.5% | 5.5% | 6.5% | 8.0% |
| 400 | 2.0% | 2.0% | 2.0% | 2.0% | 2.5% | 3.5% | 4.0% | 5.0% | 6.0% |
| 500 | 2.0% | 2.0% | 2.0% | 2.0% | 2.0% | 2.5% | 3.0% | 4.0% | 5.0% |
SME Mining Engineering Handbook, p. 963. A blank cell means the combination is not published: that curve is too tight for that speed. The calculator reads conservatively, taking the tighter radius and the higher speed when your values fall between rows.
Maximum rate of superelevation change on tangents
| Truck speed, mph | Change per 100 yd of tangent, in./yd |
|---|---|
| 15 | 9.35 |
| 20 | 9.00 |
| 25 | 8.28 |
| 30 | 7.20 |
| <40 | 5.76 |
SME Mining Reference Handbook, 2nd ed., p. 326, reproduced with the printed units exactly as published. This one is not computed for you. How the rate converts into a transition length depends on how your own standard applies it, and guessing at an interpretation of the published units is how a design ends up confidently wrong.
Rolling resistance by road surface
| Ground surface | Equivalent extra % grade |
|---|---|
| Gravel, well compacted, dry, free of loose material | 2.0 |
| Gravel, not firmly compacted but dry | 3.0 |
| Gravel, loose | 10.0 |
| Mud with firm base | 4.0 |
| Mud with soft spongy base | 16.0 |
| Sand, loose | 10.0 |
| Snow, packed | 2.5 |
| Dirt, smooth, hard, dry, well maintained, free of loose material | 2.0 |
| Dirt, soft, unplowed, poorly maintained | 4.0 |
| Dirt, soft plowed | 8.0 |
| Dirt, deeply rutted | 16.0 |
SME Mining Reference Handbook, 2nd ed., p. 327.
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Worked with the values this page loads with, so the method can be checked against the cited source without entering anything. Change any input above and the calculator recomputes; the numbers below stay as a fixed reference case.
- 24.2
- 49
- 6.0%
| Widest vehicle | 6.00 m | truck specifications, p. 320 |
| × 2-lane factor | × 3.5 | road width table, p. 323 |
| = straight running width | 21.0 m | |
| × curve widening | × 1.153 | interpolated between 45 m and 60 m, p. 324 |
| = running width through the bend | 24.2 m | |
| Superelevation | 6.0% | 50 m radius at 20 km/h, p. 963 |
| Brake reaction time | 2.75 s | from 246,500 lb GVW, p. 319 |
| + driver reaction time | 1.50 s | p. 319 |
| = total time before braking | 4.25 s | |
| Speed at perception | 5.56 m/s | 20.0 km/h |
| Distance run at speed | 23.6 m | V₀ × t |
| + gravity during that time | 7.1 m | ½ g t² sin θ, on a 8.0% descent |
| Speed once braking starts | 8.88 m/s | V₀ + g t sin θ |
| + braking distance | 18.2 m | friction 0.30 less slope 0.080 |
| = stopping distance | 48.9 m | Eq. 13.1, p. 319 |
| Sight distance required | 48.9 m | must stop within it, p. 319 |
| Limit to check against | 61 m (200 ft) | British Columbia Dept of Mines, p. 321 |
| Rolling resistance | 2.0% | road surface, p. 327 |
| Total resistance climbing out | 10.0% | 8.0% grade + 2.0% rolling |
Estimating aid only. This is not an engineering design and not a substitute for the judgment of a competent or qualified person. Verify every result against the cited source and your own site conditions. Full terms and disclaimer.