Contact

GlossaryCalls residents encounter

Traffic collision

A traffic collision is a motor-vehicle crash recorded under a stated reporting system. Learn why crash counts differ from vehicles, people injured, dispatches, and fault findings.

A traffic collision is a crash involving a motor vehicle, recorded under the source's reporting definitions. It can involve another vehicle, a person, an object, or another harmful event covered by the system. A collision record does not by itself assign legal fault. Reporting thresholds and inclusion rules determine which crashes appear in a particular dataset.

Several records can describe one crash

A collision can produce dispatch events for police, fire, and emergency medical services, a police crash report, and other records. Those records concern different functions. Counting each responding agency's entry as a separate collision can overstate the underlying number of crashes.

NHTSA's Crash Report Sampling System, or CRSS, uses a sample of police-reported crashes. Its eligibility rules require an official police report, a motor vehicle traveling on a trafficway, and resulting damage, injury, or death. Those are rules for that statistical system, not a definition of every local call category. NHTSA CRSS explanation

A dispatch entry can begin before those facts are established. An initial injury classification can also change when more information becomes available.

Example

Hypothetical example: Two cars collide at an intersection. Police and a fire unit respond, and one passenger receives medical assistance. The records contain one crash report, two vehicle records, three involved-person records, and separate response assignments.

The example contains one collision, not two because there were two cars or several because more than one service responded. A person receiving assistance is not automatically a fatality or a hospital admission. Each outcome needs the relevant field and source definition.

Common confusion

A traffic stop is an enforcement or investigative contact. A traffic collision is a crash event. Hit-and-run concerns a participant's departure under circumstances addressed by applicable law; it adds a separate issue rather than identifying who caused the impact.

“Accident” is another common record label. Its use should not be treated as a legal determination that nobody was responsible or that the crash was unavoidable.

Reading coverage and severity

Check whether the dataset covers police-reported crashes, all dispatched collision requests, injuries, fatalities, or another subset. Local reporting requirements can depend on injury or damage thresholds; Illinois publishes its own requirements, demonstrating why a national threshold should not be assumed. For trends, identify report year, event date, later revisions, and severity definitions before comparing values. Illinois crash-report guidance

Sources