The first set of data provided below is time runs performed by the DOT. Whereby they sat in their car through the corridor with a stopwatch. The second set is INRIX data. Take note of the max times seen by DOT and the max times seen by INRIX.
Time Runs: Provided by DOT To Taskforce
Not exactly sure what to attribute this to as we do not have the INRIX algorithm. It may be there may be quite significant variation within an hour (as you can see in time trials). Rest assured though, if you felt like it took a long time, so did the DOT!