Fix SumoTrafficSimulation route transfer.

[Gamenot]

Closes #2011

[Adaickalavan]

A note on self._traci_conn.vehicle.getRoute(vehicle_id)

The TraCI getRoute method returns edge ids which form the vehicle's route, but any junctions in the route are not included. Hence, total route distance calculation using getRoute method results in a shorter distance.

[Gamenot]

In the public facing method we should be resolving it to a full route using the road map.

[Adaickalavan]

The following original issues appears to be resolved by this PR.

• Issue-1: In all remaining steps within that episode, both SumoTrafficSimulation and LocalTrafficProvider appear to be managing "Leader-007".
• Issue-2: The destination road of "Leader-007" appears to have changed from E4 under SumoTrafficSimulation control to E2.224.85 when controlled by LocalTrafficProvider.

Below we use the public methods of SumoTrafficSimulation to compute the route distance.

route = traffic_sim.route_for_vehicle(vehicle_name)
for r in route.road_ids:
    print(r)
dist_tot = route.road_length

• Prior to this PR, the public method route_for_vehicle had internally called self._traci_conn.vehicle.getRoute(vehicle_id) which resulted in it returning a shorter route distance.
• Now, including code changes in this PR, the public methods above still appear to return shorter route distance and does not include junctions in the route.

[Gamenot]

Interesting, I was under the assumption that RoadMap.route_from_road_ids(road_ids) would resolve the full route.

[Adaickalavan]

Tracing the call chain, we see roads added without resolving junctions.
SumoTrafficSimulation.route_for_vehicle() -> SumoRoadNetwork.route_from_road_ids() -> SumoRoadNetwork.Route.from_road_ids()

SMARTS/smarts/core/route_cache.py

Lines 70 to 80 in 23bb395

	@classmethod
	def from_road_ids(
	cls, road_map: RoadMap, road_ids: Sequence[str]
	) -> "RouteWithCache":
	"""Factory to generate a new RouteWithCache from a sequence of road ids."""
	route = cls(road_map)
	for road_id in road_ids:
	road = road_map.road_by_id(road_id)
	assert road, f"cannot add unknown road {road_id} to route"
	route._add_road(road)
	return route

Similarly, junctions appear to be excluded resulting in a shorter distance in the public method of Smarts traffic provider LocalTrafficProvider.route_for_vehicle(vehicle_name).

We may merge this PR, and track this issue in a separate thread.

[Gamenot]

I have a fix for getting the full route.

[Gamenot]

This may still result in a shorter length perhaps but the junctions will be included.

[Adaickalavan]

The fixed SumoTrafficSimulation.route_for_vehicle().road_length now returns the full length of all the roads (including junctions) in the route, ignoring the starting offset.

[Gamenot]

There should be some consideration in the future if to add the initial and end offsets as necessary attributes of a route.