Anonymous probe vehicle data are currently being collected on major interstates and arterials throughout the United States. Probe data are used to assign average speeds to pre-define roadway segments of varying lengths. These segments are known as Traffic Message Channels (TMCs).Through the analysis of this probe data for each TMC, transportation agencies have been making progress in the development of agency wide performance measures to better plan and manage spatially distributed infrastructure assets (1, 2). One widely accepted performance measure is travel time reliability, which is calculated along a series of TMC segments that collectively makes up a corridor. When consistent travel times are not achieved, due to incidents or recurring periods of congestion, it is desirable to understand the time and frequency of these increased travel time incidents to better manage the system.