TRN-21

AASHTO equivalent single-axle load

LEF = (P / 80)^4. One 80 kN axle is one ESAL on a flexible pavement.

Reading speed

PavementAASHTO ESAL

Governing equation

\mathrm{LEF}=(P/80)^4

where

P: Axle load (kN)
n: Axle count / day (—)
LEF: Load equivalency (—)
W_{18}: Daily ESAL (ESAL/d)

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-21 — AASHTO equivalent single-axle load) is the form associated with AASHTO ESAL. Working symbols: $P$ , $n$ $\rightarrow$ $LEF$ , $W_{18}$ . The fourth-power law from the AASHO Road Test. Rigid pavements use an exponent near 4.2–4.5.

Purpose

Purpose: compute

LEF

W_{18}

from

P

n

in Transport via

\mathrm{LEF}=(P/80)^4

LEF = (P / 80)^4. One 80 kN axle is one ESAL on a flexible pavement. Use it when a real transport question must be answered in SI before a code check.

Live realistic example

In symbols

Live case. Given

P = 100.000\,\mathrm{kN}

n = 400.000\,\mathrm{—}

, the governing relation

\mathrm{LEF}=(P/80)^4

yields

LEF = 2.441\,\mathrm{—}

W_{18} = 977\,\mathrm{ESAL/d}

. An axle, a 80 kN reference, a load equivalency. Move a slider: the numbers are this situation, not a canned story.

Calculator

Inputs

Axle load P100 kNAxle count / day n400 —

Outputs

Load equivalency LEF2.441 —
Daily ESAL W_{18}977 ESAL/d

Reading speed

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Narration of this film

An axle, a 80 kN reference, a load equivalency.

The fourth-power law from the AASHO Road Test. Rigid pavements use an exponent near 4.2–4.5.

Reading speed

Watch on YouTube