49 CFR §674.23

1. (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.
2. (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.