Dinosaur Trackway Speed Reconstruction

Trackway Presets

Fossil Measurements

Hip height h (leg length) 1.00 m

Stride length SL (print-to-print, same foot) 2.60 m

Track width (trackway gauge) 0.30 m

Reconstructed Gait

Speed

-- m/s

Speed (km/h)

Relative stride SL/h

Froude number

Gait classification

How it works

Fossil trackways preserve two directly measurable quantities: the stride length SL (the distance between successive footprints of the same foot) and, from the footprint size, an estimate of hip height h (leg length is roughly 4× footprint length for most bipedal dinosaurs). R. McNeill Alexander (1976) showed that dynamically similar animals — those moving with the same dimensionless speed — share the same dimensionless stride length, which lets a footprint speed be recovered without ever seeing the animal move:

Dimensionless speed:      u = v / sqrt(g·h)
Dimensionless stride:     SL/h ≈ 2.3 · u^0.3   (empirical, from living animals)

Solving for v gives Alexander's trackway equation:
  v = 0.25 · g^0.5 · SL^1.67 · h^-1.17

g = 9.81 m/s² · SL, h in metres · v in m/s

The Froude number Fr = v²/(g·h) is the same dimensionless speed squared. It classifies gait the way it does for any legged animal, from a walking human to a walking dinosaur:

SL/h < 2.0 — walk, a statically stable inverted-pendulum gait.
2.0 ≤ SL/h < 2.9 — brisk walk / trot transition.
SL/h ≥ 2.9 — running gait (Fr typically > ~2.5), an unstable bouncing gait with an aerial phase.

Move the sliders to match a real trackway's measurements — the walker's stride timing and footfall spacing on the ground below update to match the speed and gait the formula predicts, exactly as a paleontologist would reconstruct locomotion from footprints alone.

Reconstructed trackmaker Footprint trackway

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