### Question
How is the "main line" defined?


### Answer
The term **main line** is defined in *49 U.S.C. § 20157* as follows -

> a segment or route of railroad tracks over which 5,000,000 or more gross tons of railroad traffic is transported annually, except that—


(A) the Secretary may, through regulations under subsection (g), designate additional tracks as main line as appropriate for this section

#### Citation:
  - *49 U.S.C. § 20157*
  - Heading: **SUBTITLE V-RAIL PROGRAMS > PART A-SAFETY > CHAPTER 201-GENERAL > SUBCHAPTER II-PARTICULAR ASPECTS OF SAFETY**

