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Two-way vehicles per day, averaged over the year.
From a traffic count or a highway authority's published data. A count taken on a single weekday is not an AADT and will usually overstate it.
Share of traffic that is heavy vehicles.
This is the input that matters. Cars contribute almost nothing to pavement damage — a passenger car is worth roughly one ten-thousandth of a standard axle. Get the truck percentage wrong and the entire design is wrong.
Average ESALs contributed by one truck.
Varies enormously by fleet: light delivery vehicles well below 0.5, loaded multi-axle articulated units above 2. Use the local highway authority's factor where one is published — a fleet-specific figure is worth far more than any default.
Share of trucks in the design direction.
0.5 on a balanced two-way road. Higher where loaded trucks run predominantly one way — a quarry haul route is the classic case, loaded out and empty back.
Share of directional trucks in the design lane.
1.0 for a single lane per direction; around 0.8-0.9 for two lanes; lower for three or more. Trucks concentrate in the nearside lane, which is why that lane fails first.
Analysis period for the structural design.
A decision rather than a measurement, and it sets how much traffic is accumulated and therefore how thick the pavement comes out. A shorter period gives a thinner structure that will need intervention sooner, which is sometimes exactly right — a haul road with a known end date, or a road whose subgrade is to be improved when the adjacent site is developed. Choose it deliberately and record why.
Compound annual growth over the life.
Compounds, so it matters more than it looks. Two percent over twenty years adds about 21% to the cumulative total against a flat assumption.
Design ESALs
2,840,000 ESALs
Standard AASHTO cumulative ESAL build-up. The answer is dominated by the truck percentage and the truck factor — both site data, neither guessable.
- Millions of ESALs
- 2.84 MESAL
- Design-lane ESALs per day
- 320 ESAL/day
- First-year ESALs
- 116,800 ESALs
- Growth factor over the life
- 24.3 ×
- Trucks per day in the design lane
- 320 trucks/day
- Uplift from growth over a flat assumption
- 21.49 %
They open the calculator with your figures already in it
Pavement Design ESAL Calculator: 2,837,933 ESALs — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
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How this was calculated
Formula source(s)
- AASHTO Guide for Design of Pavement Structures: damage scales approximately with the fourth power of axle load relative to the 18,000 lb (80 kN) standard axle
- Design ESAL = AADT × truck % × truck factor × directional distribution × lane distribution × 365 × growth-adjusted design years
Inputs used
- AADT (annual average daily traffic)
- 8000
- Trucks (% of AADT)
- 8
- Truck factor (ESAL per truck)
- 1
- Directional distribution
- 0.5
- Lane distribution
- 1
- Design life (years)
- 20
- Annual traffic growth (%)
- 2
Intermediate steps
- Millions of ESALs
- 2.84 MESAL
- Design-lane ESALs per day
- 320 ESAL/day
- First-year ESALs
- 116,800 ESALs
- Growth factor over the life
- 24.3 ×
- Trucks per day in the design lane
- 320 trucks/day
- Uplift from growth over a flat assumption
- 21.49 %
Confidence note: Standard AASHTO cumulative ESAL build-up. The answer is dominated by the truck percentage and the truck factor — both site data, neither guessable.
What this calculation does not cover
- Produces the traffic loading only. Converting ESALs into a pavement thickness needs subgrade strength, layer coefficients, reliability, serviceability loss and drainage — a separate design.
- The fourth-power damage relationship is an empirical approximation from the AASHO Road Test. It is standard practice and it is still an approximation.
- Construction traffic during the works is not included and can be a significant share of an access road's whole-life loading.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-08-27 · in the site-wide review of 2026-09-06 · v1.0.0
Regulatory standards & verification citations2
- AASHTO Guide for Design of Pavement Structures: damage scales approximately with the fourth power of axle load relative to the 18,000 lb (80 kN) standard axle
- Design ESAL = AADT × truck % × truck factor × directional distribution × lane distribution × 365 × growth-adjusted design years
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