Exposure / Traffic Volume Data
The denominators. Traffic volume and vehicle-miles-traveled data that turn raw crash counts into rates.
FHWA's vehicle miles traveled (VMT) tables, broken out by state and road type. This is exposure data — the denominator that turns raw counts into meaningful rates. A death toll means little without the miles driven behind it; VMT lets analysts express fatalities per 100 million miles traveled rather than as raw totals.
Counts of registered vehicles by county, which serve as another exposure denominator — allowing the relative risk of different vehicle types (motorcycles, trucks) to be assessed against how many are actually on the road.
TxDOT's real time traffic volume system, reporting annual average daily traffic (AADT) and vehicle classification counts — including heavy trucks via weigh in motion — across the state highway network, mapped in GIS.
Other categories