yard track sizes

hi, I am in the planing stages of a modern hump/classification yard in HO scale. The threw tracks will be code 83. My questions are the following, 1. Would the A/D tracks be code 83 or 70? 2.Would all classification and engine service track be code 70? 3. What would be the correct code for the actual over the hump track? (using retarders) Gary Taylor

If I had to wager a guess, I would say that the A/D tracks would be 83, and the yard and engine tracks 70. The actual hump track would probably be 83, as it would see quite a bit of use.