# Per the ME Pavement Design Guide MOP, Section 5.3.6, Eq 5-18b, how is p02 assumed if not entered in Pavement ME?

The MOP, equation 5-18b calls for p02, which the MOP describes as the "Percent passing the 0.02 mm sieve". I assume that this is the percent passing for the subgrade. We only input down to the p200 for our subgrades. For example, our clay entry is the following:

• 3/8” = 99.9
• No. 4 = 99.5
• No. 10 = 97.7
• No. 20 = 96.0
• No. 40 = 90.7
• No. 100 = 68.3
• No. 200 = 57.5

Therefore, how is Pavement ME calculating the p02 input for us of the site factor (SF)?

Note that if 0 is assumed, then the equation would have an error because LN(0) is undefined (ie. no value), so I assume that some value must be assumed.

• Welcome to Engineering! I'm not a pavement engineer, so don't know. However, I'd assume they adopt the "worst case". I assume a high SF is bad (since it's proportional to age), so it seems the worst case would be to assume that $p_{02} = p_{200}$. – Wasabi Jul 16 at 14:33