  We consider a freight platform that serves as an intermediary between
shippers and carriers in a truckload transportation network. The platform's
objective is to design a mechanism that determines prices for shippers and
payments to carriers, as well as how carriers are matched to loads to be
transported, to maximize its long-run average profit. We analyze three types of
carrier-side mechanisms commonly used by freight platforms: posted price,
auction, and a hybrid mechanism where carriers can either book loads at posted
prices or submit their bids. The proposed mechanisms are constructed using a
fluid approximation model to incorporate carrier interactions in the freight
network. We show that the auction mechanism has higher expected profits than
the hybrid mechanism, which in turn has higher profits than the posted price
mechanism. Thus, the hybrid mechanism achieves a trade-off between platform
profit and carrier waiting time. We prove tight bounds between these mechanisms
for varying market sizes. The findings are validated through a numerical
simulation using industry data from the U.S. freight market.
