I didn't know passenger traffic had the twice a week requirement. I always though it was solely based on Class of Track. I know in San Diego are they run the commuter tracks 3 times a week, but that is just local policy, not any kind of regulation.
It's from § 213.233(c)...
Each track inspection shall be made in accordance with the following schedule—
Class of track: Excepted track and Class 1, 2, and 3 track
Type of track: Main track and sidings
Required frequency: Weekly with at least 3 calendar days interval between inspections, or before use, if the track is used less than once a week, or twice weekly with at least 1 calendar day interval between inspections, if the track carries passenger trains or more than 10 million gross tons of traffic during the preceding calendar year.
Class of track: Excepted track and Class 1, 2, and 3 track
Type of track: Other than main track and sidings
Required frequency: Monthly with at least 20 calendar days interval between inspections.
Class of track: Class 4 and 5 track
Required frequency: Twice weekly with at least 1 calendar day interval between inspections.
http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&rgn=div5&view=text&node=49:4.1.1.1.8&idno=49#49:4.1.1.1.8.6.5.2
Although I made a mistake, I'm sure the track we're talking about in this thread is class 4, so passenger traffic is irrelevant.