Critical Accident Rate:

The following formula is used to calculate critical rates:

Critical rate variables:

Variable name:                 Represents:        

CriticalRate =                 For intersections/nodes: Accidents per million vehicle miles/kilometers. For segments: Accidents per million vehicles.        

AvgRate                 Average accident rate for the entire population of segments/nodes or intersection in the study.        

K                 Probability constant (default 2.576 – 99.5% level of confidence)        

M                 For intersections/nodes: Millions of vehicles. For segments: Millions of vehicle miles.        

Days =                 Number of days in the study (diagram)