Quickly estimate the required pavement layer thicknesses for flexible pavements using the AASHTO 1993 design methodology. Enter your expected traffic load (ESALs), subgrade strength, and reliability requirements to generate recommended asphalt, base, and subbase thicknesses in inches. See Definitions of the inputs and outputs provided below prior to using this tool.
This tool is ideal for civil engineers, transportation planners, and contractors working on road design.
Pavement Design Calculator (AASHTO 1993)
📥 Pavement Design Inputs
- ESALs (Equivalent Single Axle Loads):
A measure of cumulative traffic loading expected over the design life of the pavement, converted into equivalent 18,000-lb axle repetitions.
➤ [Use this converter] to calculate ESALs from traffic volume and axle distribution. - Subgrade CBR (%):
California Bearing Ratio — a test-based value representing subgrade strength.
Typical range: 2–15% for Pakistani soils. - Design Reliability (%):
The confidence level that the pavement will perform satisfactorily.
Use 75–95% depending on road classification (e.g., rural road vs. highway). - Standard Deviation (So):
AASHTO recommends 0.35–0.45 depending on variability in materials and construction. Use 0.45 if unsure. - Serviceability Loss (ΔPSI):
Difference between initial and terminal serviceability. Default is 1.7.
📤 Pavement Layer Outputs
The calculator returns:
- Asphalt Layer Thickness (in)
- Base Course Thickness (in)
- Subbase Thickness (in)
These are calculated using empirical correlations and layer coefficient values as per AASHTO 1993. Adjustments may be needed based on local materials, climate, and specifications.
⚠️ Disclaimers
- This is a preliminary planning tool. It does not replace detailed geotechnical investigations or official pavement design procedures.
- For final design, always consult with a licensed engineer and local highway authorities.
- Assumptions in this tool are based on generalized values from AASHTO and may not reflect site-specific conditions.