Strange itineraries when routing based on arrival time

[tibobliss]

Routing using the Arrival time parameter seems to introduce distorsions in the trip itinerary chosen by trRouting. For instance:

Here is a random trip using a random starting time (7:11). Notice how the proposed itinerary below includes a 3-minute walk from the last stop for a total trip time of 41 minutes and an arrival at 7:52.

If we switch to using the arrival time and set it to 7:53 (to account for any rounding), we get the itinerary below. Notice how the last stop changes to the next one on the route, but we still get a 3-minute egress walk and a total trip time of 41 minutes, arriving at 7:52.

Now, if we set the arrival time to 8:00, we get the strange behavior illustrated below. The starting time is the same as the 2 other scenarios, but the arrival time is 4 minutes later at 7:56, for at total trip time of 46 minutes. Notice how the egress stop is farther down the route and the itinerary then backtracks on foot via a 7-minute walk.

It seems like trRouting tries to arrive as close as possible to the Arrival time parameter, even if that introduces extra vehicle time and walking time.

[greenscientist]

Moved this issue to TrRouting, since the problem is at that level