Guides

• How FARS counts a fatal crash: the 30-day rule, public roads only, what "involving alcohol" and "speeding-related" mean, and what the file does not contain.
• When a new year of data arrives: why the latest year here is 2024, NHTSA's release cycle and how a year is revised.
• Road function classes: interstate, freeway, principal and minor arterial, collector and local, as FHWA defines them.