California Code, Public Utilities Code - PUC § 765

(a) When the federal National Transportation Safety Board (NTSB) submits a safety recommendation letter concerning rail safety to the commission, the commission shall provide the NTSB with a formal written response to each recommendation no later than 90 days after receiving the letter.  The response shall state one of the following:

(b) If the NTSB issues a safety recommendation letter concerning any commission-regulated rail facility to the United States Department of Transportation, the Federal Transit Administration, a commission-regulated rail operator, or the commission, or if the Federal Transit Administration issues a safety advisory concerning any commission-regulated rail facility, the commission shall determine if implementation of the recommendation or advisory is appropriate.  The basis for the commission's determination shall be detailed in writing and shall be approved by a majority vote of the commission.

(c) If the commission determines that a safety recommendation made by the NTSB is appropriate, or that action concerning a safety advisory is necessary, the commission shall issue orders or adopt rules to implement the safety recommendation or advisory as soon as practicable.  In implementing the safety recommendation or advisory, the commission shall consider whether a more effective, or equally effective and less costly, alternative exists to address the safety issue that the recommendation or advisory addresses.