Lane saturation

How to calculate “Lane saturation” from AADT?
iRAP Methodology uses lane saturation to calculate SRS, but we only have AADT data for all lanes.
Is it correct to divide AADT to “number of lanes” and consider 1 if it is 18000 and consider 0 if it is 2000?
I would be thankful if somebody could help me on this.

I’m not quite sure about the second part of your question but its correct to assume that the AADT is divided equally between the lanes in the iRAP model.