Create back-to-back trips

This document describes how to create a back-to-back trip, set the correct fields, and assign it to a vehicle to fulfill. It assumes you have set up Fleet Engine, you have created vehicles, have a working driver app, and optionally, a consumer app. You should also be familiar with the various trip scenarios available for on-demand trips. See the following related guides for that:

Set up Fleet Engine
Create a vehicle
Trip scenarios in the On-demand trips overview

Trip creation basics

This section describes the request details necessary for creating a trip in Fleet Engine. You issue a creation request using either gRPC and REST.

CreateTrip() method: gRPC or REST
CreateTripRequest message: gRPC only

Trip Fields

Use the following fields to create a trip in Fleet Engine. You can use different fields for the different kinds of trips: single- or multi-destination, back-to-back, or shared pooling trips. You can supply the optional fields when you create the trip, or you can set them later when you update the trip.

Trip fields
Name	Required?	Description
parent	Yes	A string that includes the project ID. This ID must be the same ID used across your entire Fleet Engine integration, with the same service account roles.
trip_id	Yes	A string that you create that uniquely identifies this trip. Trip IDs have certain restrictions, as indicated in the reference.
trip_type	Yes	Set the TripType to the following values for the trip type you're creating: Single destination: Set to `SHARED` or `EXCLUSIVE`. Multi-destination: Set to `EXCLUSIVE`. Back-to-back: Set to `EXCLUSIVE`. Shared pooling: Set to `SHARED`.
pickup_point	Yes	The trip's point of origin.
Intermediate destinations	Yes	Multi-destination trips only: The list of intermediate destinations that the driver visits in between pickup and drop-off. As with `dropoff_point`, this field can also be set later by calling `UpdateTrip`, but a multi-destination trip by definition contains intermediate destinations.
vehicle_waypoints	Yes	Shared-pooling trips only: This field supports interleaving the waypoints from multiple trips. It contains all of the remaining waypoints for the assigned vehicle, as well as the pickup and drop-off waypoints for this trip. You can set this field by calling `CreateTrip` or `UpdateTrip`. You can also update vehicle waypoints through the `waypoints` field with a call to `UpdateVehicle`. The service does not return this information on `GetTrip` calls due to privacy reasons.
number_of_passengers	No	The number of passengers on the trip.
dropoff_point	No	The trip's destination.
vehicle_id	No	The ID of the vehicle assigned to the trip.

Example: create a back-to-back trip

The following demonstrates how to create a back-to-back trip and assign it to a vehicle. In this scenario, trip creation is the same as for a single-destination trip. It's only later that you create another trip and assign it to a vehicle with an already-active trip.

// A vehicle with ID 'my-vehicle' is already created and it is assigned to a trip with ID 'current-trip'.

static final String PROJECT_ID = "my-rideshare-co-gcp-project";
static final String VEHICLE_ID =" my-vehicle";
static final String TRIP_ID = "back-to-back-trip");

TripServiceBlockingStub tripService = TripService.newBlockingStub(channel);

String parent = "providers/" + PROJECT_ID;

Trip trip = Trip.newBuilder()
    .setTripType(TripType.EXCLUSIVE)
    .setPickupPoint(
        TerminalLocation.newBuilder().setPoint(
            LatLng.newBuilder()
                .setLatitude(-6.195139).setLongitude(106.820826)))
    .setDropoffPoint(
        TerminalLocation.newBuilder().setPoint(
            LatLng.newBuilder()
                .setLatitude(-6.1275).setLongitude(106.6537)))
    .setVehicleId(VEHICLE_ID)
    .build();

// Create trip request
CreateTripRequest createTripRequest = CreateTripRequest.newBuilder()
    .setParent(parent)
    .setTripId(TRIP_ID)
    .setTrip(trip)
    .build();

// Error handling.
try {
  // Fleet Engine automatically assigns a 'waypoints' list to the trip containing
  // the vehicle's current trip waypoints.
  Trip createdTrip =
      tripService.createTrip(createTripRequest);
} catch (StatusRuntimeException e) {
  Status s = e.getStatus();
  switch (s.getCode()) {
    case ALREADY_EXISTS:
      break;
    case PERMISSION_DENIED:
      break;
  }
  return;
}

Update back-to-back trips

When you assign a vehicle for a back-to-back trip, you assign a trip to a vehicle even if it has already been assigned one.

Any trip created in Fleet Engine must be assigned to a vehicle in order for Fleet Engine to calculate trip ETAs and track it. You can do this either during trip creation or later when you update the trip.

After you assign the trip to a vehicle, Fleet Engine automatically adds the waypoints associated with the back-to-back trips to the vehicle's waypoints field. A trip's remainingWaypoints field contains a list of all of the waypoints, including those from other trips that will be visited before the trip's drop-off.

For example, consider two back-to-back trips: Trip A and Trip B. The vehicle has picked up the consumer for Trip A, and while en route to the drop-off location, the driver receives a request to pickup another consumer for the next trip, Trip B.

Calling getVehicle() returns remainingWaypoints that contain:
A _Drop-off → B _Pickup → B _Drop-off.
Either getTrip() or the onTripRemainingWaypointsUpdated callback for Trip A returns remainingWaypoints that contain:
A _Drop-off.
Either getTrip() or the onTripRemainingWaypointsUpdated callback for Trip B returns remainingWaypoints that contain:
A _Drop-off → B _Pickup → and B _Drop-off.