TransAm 2016 - www.transambikerace.com

Might just be me, but TransAm rules seem to read in a disjointed way compared to TCR. Says it's modified from the Tour Divide ruleset which states

Advancing (forward) on the route by any means other than one's own
pedal power is strictly prohibited. No drafting. Use of any type of
air scoop or umbrella sail intended to harness wind power is also
prohibited. TD is a solo challenge, however, racing in the company of
other challengers is tolerated. Again, no drafting, and each rider
must maintain separate gear.

But the only mention of drafting on TransAm is in relation to pairs (a pair can draft each other, but not other pairs)

http://transambikerace.com/rules/