AASHTO 93 Pavement Structural Design

Metric units (mm, MPa). Implements the 1993 AASHTO Guide design equations for flexible and rigid pavements.

Traffic & Reliability

Design ESALs (W18)

Reliability R%

Std deviation Sₒ

0.40–0.50 typical

ΔPSI (po − pt)

e.g. 4.2 − 2.5 = 1.7

Subgrade MᴿMPa

Layer Coefficients & Drainage

a₁ (AC)

a₂ (Base)

a₃ (Subbase)

0 to skip

m₂ (Base)

m₃ (Subbase)

E baseMPa

Min D₁ (AC)mm

Min D₂ (Base)mm

Min D₃ (Subbase)mm

Results

Z_R

-1.645

SN required

4.79

SN provided

5.46

log₁₀ W18 (predicted)

7.103

Asphalt (D₁)

165 mm

Contribution SN = 2.86

Base (D₂)

355 mm

Contribution SN = 1.96

Subbase (D₃)

150 mm

Contribution SN = 0.65