TRN-03

AASHTO equivalent single-axle load

Load equivalency ≈ (L/80 kN)^4 for flexible pavements.

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PavementAASHTO 1993

Governing equation

W_{18}=\left(\dfrac{L}{80\,\mathrm{kN}}\right)^4

where

L: Axle load (kN)
W_{18}: Equivalency factor (ESAL)

Lecture brief

Historical brief

Highway and traffic theory crystallized with Greenshields’ 1935 speed–density line, then AASHTO stopping sight and equivalent axles. The lab is that operational arithmetic of flow, braking and pavement load. This sheet (TRN-03 — AASHTO equivalent single-axle load) is the form associated with AASHTO 1993. Working symbols: $L$ $\rightarrow$ $W_{18}$ . The AASHTO road test showed pavement damage scales roughly with the fourth power of axle load, the origin of the ESAL.

Purpose

Purpose: compute

W_{18}

from

L

in Transport via

W_{18}=\left(\dfrac{L}{80\,\mathrm{kN}}\right)^4

Load equivalency ≈ (L/80 kN)^4 for flexible pavements. Use it when a real transport question must be answered in SI before a code check.

Live realistic example

In symbols

Live case. Given

L = 100.000\,\mathrm{kN}

, the governing relation

W_{18}=\left(\dfrac{L}{80\,\mathrm{kN}}\right)^4

yields

W_{18} = 2.441\,\mathrm{ESAL}

. Single axle, flexible pavement, fourth-power snapshot. Move a slider: the numbers are this situation, not a canned story.

Calculator

Inputs

Axle load L100 kN

Outputs

Equivalency factor W_{18}2.441 ESAL

Reading speed

Watch on YouTube

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Narration of this film

Single axle, flexible pavement, fourth-power snapshot.

The AASHTO road test showed pavement damage scales roughly with the fourth power of axle load, the origin of the ESAL.

Reading speed

Watch on YouTube