Glossary

Causative factor

The combination of simultaneous and sequential factors without any one of which the result could not have occurred.

Contributing factor

Any circumstance contributing to a result without which the result could not have occurred.

Roundabout

A one-way circular intersection in which entering traffic yields to traffic already in the circle and specifically designed to slow the speed of traffic by using deflection and small radius circles.

Speed

Rate of progress, or change in position, usually without regard to direction; distance divided by time (if speed is constant); a scalar quantity which refers to how fast an object is moving; generally referred to in miles or kilometers per hours (mph or km per hr [km/h]).

Speed Limit, Absolute

A specified numerical value, the exceeding of which is always in violation of the law, regardless of the conditions or hazards involved.

Speed Limit, Differential

Speed limits that differ by vehicle type or time of day (e.g., day and night)

Speed Limit, Variable

Speed limits that change based on road and traffic conditions

Speed Management

Application of various methods to achieve safe and appropriate travel speeds

Speed zone

A speed limit posted on a section of road on the basis of a traffic engineering investigation that determined that the statutory limit which would otherwise apply is too high or too low

Speeding

The act of exceeding the legal speed limit or driving too fast for conditions

Speeding-related

A crash in which a driver is charged with a speeding-related offense or if the reporting officer indicated that racing, driving too fast for conditions, or exceeding the posted speed limit is a contributing factor in the crash.

Traffic calming

Combination of mainly physical measures intended to reduce traffic speed and enhance the street environment for non-motorists