Travel times for corridor segments don't sum to whole corridor

[Nate-Wessel]

Example query: results.csv

If corridor is subdivided into smaller corridors, the travel times for the sub-corridors don't sum cleanly to the travel time for the whole corridor. The difference is big enough that it doesn't seem to just be rounding / floating point error.

Need to at least identify the source of this issue so it can be explained.