Time Space Diagram

Questions and discussions about operating Tru-Traffic

Moderator: bullock

Time Space Diagram

Postby DavidCox » Thu Sep 12, 2019 6:40 pm

Good Afternoon,
I have set up my and verified all of my timing information including the reference point, offsets and splits. I have also verified my GPS coordinates. My concern is that when I make my trips I keep getting stopped when I should be on the Green Bands and then drive right through the Red Bands. This is causing me quite a bit of trouble since I am attempting to optimize my offsets on the corridor.

Is there something simple I am missing?


Thank you,

Eastchester_DeepRiver to Gallimore Dairy.Dgm
This is the file with the Time Space Diagram I am referencing,
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Re: Time Space Diagram

Postby bullock » Fri Sep 13, 2019 7:14 am

It looks like a couple of things are going on here.
  • The clock synchronization (specifying a signal cycle start time) that was set and in effect when the trip logs were originally recorded, differs from each of the two clock synchronizations that are now associated with the two different timing plans (PLAN 6 and 6/1/1). And
  • At least one of the timing plans shows a different offset at Mendenhall Oaks Parkway than what was running on 9/11/2019 (the day of the trip log).

Notice that if you select timing plan "6/1/1", then in View: GPS View: Trip Logs, double click on the trip log and set the Signal Cycle Start Time to the clock synchronization for PLAN 6, then most of the runs seem to go through the intersections when the signal could have been green, accounting for possibly early gap outs on the side street. See the attached image.
But if you switch to timing plan PLAN 6, still using the clock synchronization for PLAN 6, then the runs cross Mendenhall Oaks Parkway very late in the green, as though the vehicles were waiting for no good reason.

To get it all to look right, we need to
  1. select (or create) a timing plan with the timings that were in effect, in the field, on 9/11/2019 (the day of the trip log),
  2. ensure that this same timing plan has its clock synchronized properly, so that when you view the Cycle Timer (View: Cycle Timer), the moving, horizontal "now" line crosses the phase transitions when you see those occur in the field, and
  3. assign to the trip log the clock synchronization of that timing plan.
Step 2. should work reliably provided either that your computer has the correct time of day (accurate to the second), or that Tru-Traffic is connected to a GPS device that is tracking and with a fix (in which case Tru-Traffic takes the time of day from the GPS device's reports, which gives it accurately as long as it has a fix). It's also assumed that your signal controllers have stable clocks, even if they're not accurate.

If oddities persist after that, let me know.

Better_synchronized_trip_log.png (109.59 KiB) Viewed 1521 times
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