49 C.F.R. § 213.233
(b) Each inspection shall be made on foot or by riding over the track in a vehicle at a speed that allows the person making the inspection to visually inspect the track structure for compliance with this part. However, mechanical, electrical, and other track inspection devices may be used to supplement visual inspection. If a vehicle is used for visual inspection, the speed of the vehicle may not be more than 5 miles per hour when passing over track crossings and turnouts, otherwise, the inspection vehicle speed shall be at the sole discretion of the inspector, based on track conditions and inspection requirements. When riding over the track in a vehicle, the inspection will be subject to the following conditions -
(c) Each track inspection shall be made in accordance with the following schedule -
| Class of track | Type of track | Required frequency |
|---|---|---|
| Excepted track and Class 1, 2, and 3 track | Main track and sidings | 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. |
| Excepted track and Class 1, 2, and 3 track | Other than main track and sidings | Monthly with at least 20 calendar days interval between inspections. |
| Class 4 and 5 track | Twice weekly with at least 1 calendar day interval between inspections. |
Note to § 213.233: Except as provided in paragraph (b) of this section, no part of this section will in any way be construed to limit the inspector's discretion as it involves inspection speed and sight distance.