A written document issued unilaterally to the Contractor by MTA. The unilateral Change Order is signed by the Contracting Office, but not by the contractor. The Change Order incorporates in the contract changes in the work. After receipt, the contractor is required to submit a proposal covering any changes caused by the Change Order, and negotiations between the MTA and the contractor will be held to price out the cost (or savings) of the changes. Alternatively, a contract change may be made by bilateral price modifications.