### Question
How does the law define diesel retrofit?


### Answer
Under *23 U.S.C. § 149*, **diesel retrofit** is defined as:

> a replacement, repowering, rebuilding, after treatment, or other technology, as determined by the Administrator

#### Citation:
  - *23 U.S.C. § 149*
  - Heading: **CHAPTER 1-FEDERAL-AID HIGHWAYS**

