In plain terms. TAR is the Department of Transportation's supplement to the FAR, adding DOT-specific acquisition rules.
Who it applies to. Contractors serving DOT and its agencies (such as the FAA).
What it requires. Comply with the FAR, then TAR additions. DOT work can involve safety-critical systems and operational data, so expect information-security and handling requirements tied to those systems.
Why it matters. Transportation systems can be safety- and security-sensitive, raising the importance of sound information protection on DOT contracts.
Citation. TAR, the Transportation Acquisition Regulation supplement to the Federal Acquisition Regulation (FAR), codified in the FAR System at Title 48 of the C.F.R.