TT&D Report - Cumulative Summary start times

Questions and discussions about operating Tru-Traffic

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TT&D Report - Cumulative Summary start times

Postby DVielkanowitz » Mon Mar 16, 2015 8:46 pm

Where do the times reported in the cumulative summary come from? They are different from the two directions that are being averaged together.

Should it report the earliest start time from either of the directions and the latest start time from either direction?
or
Could it report the earliest start time from either of the directions and the latest end time from either direction (latest start time + CTT) to give user the full duration of the reported data?
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Re: TT&D Report - Cumulative Summary start times

Postby bullock » Mon Mar 16, 2015 10:08 pm

The range of times shown in the the cumulative summary table header for each direction of travel includes the starting times (only) of all the runs summarized in that direction of travel. It does not include the times the trip log(s) started recording, but rather the times the runs started (i.e., the times the trip log(s) entered the artery at the first intersection). Also, it does not include the duration of the runs or (equivalently) the ending times of the runs.

Should it report the earliest start time from either of the directions and the latest start time from either direction?


Yes. More specifically, the EB cumulative summary reports the earliest start time among the EB runs (only) and the latest start time among the EB runs. Similarly for the WB cumulative summary. And the bidirectional cumulative summary reports the earliest start time among both the EB and WB runs and the latest start time among both the EB and WB runs.

or
Could it report the earliest start time from either of the directions and the latest end time from either direction (latest start time + CTT) to give user the full duration of the reported data?


No. The only indication of the end times is the CTT column, which can include rows for mean CTT, minimum CTT, and/or maximum CTT (as well as other possible statistics). But here, the minimum CTT is decoupled from the start time of whichever particular run has the minimum CTT, so while we can say that the end times are within the range of (the earliest start time + minimum CTT) to (the latest start time + maximum CTT), without looking at the details tables, we don't know if there actually is a run that ended at either of those two times. That is, it's possible that the end times all fall within a tighter range than that, but we don't know without looking at the details tables.

If you think it would help for the headers of the cumulative summary tables to give more details (for example, if you think they should give the earliest and latest end times, or the minimum & maximum durations regardless of whether the report includes rows showing minimum and maximum CTT), I'd be interested to hear the feedback.

Regards.
Greg
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