The term contract rate is misleading. To an outsider, the word contract rate suggests that it is a binding contract, a situation in which if the rate is not honored, you could sue the other party. This is not the way it works. Often contract rates are quoted with the best intentions of the two parties. But either party has the right to take that rate, reject it, or rebid it. There is nothing fixed in any of this, outside of the dedicated contract market. Regardless, most rates are fixed for some period of time. Even if the cheapest carrier rejects a load and it goes to the next carrier in line, the rate paid by the shipper for freight has likely increased, but the shipper is said to still operate in the contract market, so long as the rate it is paying the second carrier was agreed to far in advance.