BNSF Intermodal Train types

BNSF Intermodal trains are designated with either Z, P or S. Am I correct in assuming the following?

S - doublestack trains (may also have trailers in wellcars and/or autoracks)
Z - TOFC/COFC trains (may also have autoracks)
P - mixed (usually have both stack cars, COFC/TOFC and autoracks)

more than that...

P - Premium Interomdal
Q - Guaranteed Intermodal
S - Stack
Z - UPS Service (Premium Guaranteed)

Avro Arrow wrote:P - Premium Interomdal
Q - Guaranteed Intermodal
S - Stack
Z - UPS Service (Premium Guaranteed)

OK, I actually knew that, but the trains are typically composed as in my first post? (IE S-trains have stack cars, whereas the others have TOFC/COFC cars?)

USRailFan wrote:

Avro Arrow wrote:P - Premium Interomdal
Q - Guaranteed Intermodal
S - Stack
Z - UPS Service (Premium Guaranteed)

OK, I actually knew that,

Obviously you didn't or you would have posted it to begin with. It's BNSF's 'official' classification of their intermodal trains.

but the trains are typically composed as in my first post? (IE S-trains have stack cars, whereas the others have TOFC/COFC cars?)

Sometimes vehicles are tacked on to intermodal trains if they need to move and there isn't enough of a demand to call a vehicle train by itself (prefix: V).