As used in this chapter, unless the context otherwise requires:
1. “Agency” means any governmental body which exercises jurisdiction over any road as provided in section 306.4.
2. “Book”, “list”, “record”, or “schedule” kept by a county auditor, assessor, treasurer, recorder, sheriff, or other county officer means the county system as defined in section 445.1.
3. “Department” means the state department of transportation.