Itinéraires avec GTFS

Question

<\/HEAD>Je cherche de l'aide pour comprendre comment planifier mes trajets en transports publics via les données GTFS que j'ai importées. <\/P> <\/P> J'ai suivi toutes les étapes du Guide de l'utilisateur, ainsi que les cours en ligne. Cependant, Network Analyst ne planifie mes trajets que sur mon fichier de rues ("Streets_UseThisOne"). Chaque fois que j'essaie de planifier sur TransitLines (ce qui semble le plus logique lorsqu'on tente de planifier des trajets en transports publics, même si ce ne sont que des lignes entre arrêts), cela me donne une erreur de non-traversabilité. Il planifie correctement sur la couche Streets_UseThisOne, mais cela ne représente pas où mes transports publics circulent réellement. <\/P> <\/P> Pour expliquer davantage mon projet : j'essaie de comparer des flux GTFS historiques avec des flux GTFS actuels. Essentiellement, le but est de comprendre comment le temps de trajet a changé au fil des années (c'est-à-dire les services de transport entre 1995 et 2005). J'aimerais pouvoir prendre deux arrêts. Un de 1995 et un de 2005 et voir comment le temps de trajet a changé, soit à cause de fermetures/améliorations routières, soit à cause du changement des itinéraires du système de transport. D'après ce que je comprends, ces outils devraient m'aider à faire cela, mais je ne semble pas être capable d'obtenir les résultats corrects. <\/P> <\/P> Est-ce que quelque chose m'échappe ?<\/P><\/BODY><\/HTML>

Melinda Morang · Answer

Okay, several things going on here...

First, you should NOT expect the transit lines produced in Add GTFS to a Network Dataset to represent that actual streets or other paths taken by the transit lines in the system.  They are simply straight lines connecting stops and are meant to represent the logical connections between stops in the transit network, NOT for accurate visualization of the transit lines.  Display Route Shapes, on the other hand, specifically uses the GTFS shapes.txt file and turns those into features for visualization on the map.  Because GTFS has somewhat of a disconnection between shapes.txt and the files that represent the schedules, it's much much much easier for Add GTFS to a Network Dataset to just use straight lines.

Next, after you corrected those problems with your network dataset's settings, did you run Build Network and re-run Get Network EIDs?  Without doing those things, the changes you made aren't fully baked into the network.

Finally, the non-traversable error to be looks like one of two things:

1) Your network has some kind of restriction attribute set up, and some roads are actually restricted (non-traversable).  Perhaps the restriction is configured incorrectly.

2) You forgot to set up the layer's network location settings according to this section of the user's guide: public-transit-tools/UsersGuide.md at master · Esri/public-transit-tools · GitHub .  As a result, sometimes the input points are being located on transit lines, and bad things are happening.

TerryKarlson · Answer

Hi Melinda,

Thank you for taking the time to help me. I heeded your advice and went through the troubleshooting guide. It turns out that my Stops_Snapped2Streets were not in "override". I adjusted this setting accordingly. Additionally, I didn't have the "Use Start Time" checked in the Analysis Settings. After also changing this setting, everything else in the troubleshooting guide seemed to be similar to what I had. However, I was still receiving inaccurate results. I decided to move onto the "None of the Above" section.

I have attached pictures that will hopefully help me explain myself. The picture below is a shot of the two stops I selected from the TransitLines layer (Green lines). Note: the red lines are my Streets_UseThisOne layer. The streets somehow got broken up or pixelated when I took a screenshot. It's not this way on the computer. The orange lines are the route shape I made using the Display GTFS Route Shapes tool. I did this to compare the "solve" tool to the actual shape. The darker orange/brown color is the route from the "solve" tool.

To explain the non-traversable error I occasionally receive. Here are my results:  As you can see, I moved stop 2 slightly to the left (more on the green TransitLines layer) and I received this message when I try to "solve" the route. I moved it back for the purpose of running through the debugging process. After moving it back, it correctly solves the two stops, but the routing is off. See below:

Here you can see that it solves the route, but it takes the route in an unusual path. The spots circled in yellow are where the route does not line up with the route shape from the Display GTFS Shape tool I used. This makes me think it is still set on routing via the Streets layer.

Any ideas?

Melinda Morang · Answer

Hello Terry.

If your results seem to be never using the transit lines, please review the probably causes and solutions listed here: public-transit-tools/TroubleshootingGuide.md at master · Esri/public-transit-tools · GitHub

If that doesn't help, could you please clarify this comment?

it gives me a non-traversable error

What is the error message, and when/where did you see it? (Example: when you clicked Solve)

Regarding your ultimate goal: Yes, this should be doable.  It's probably best if you have two separate networks, one for the older data and one for the newer data.