49 CFR 674.23: Confidentiality of information.

(a) A State, an SSOA, or an RTA may withhold an investigation report prepared or adopted in accordance with these regulations from being admitted as evidence or used in a civil action for damages resulting from a matter mentioned in the report.

(b) This part does not require public availability of any data, information, or procedures pertaining to the security of a rail fixed guideway public transportation system or its passenger operations.