require matching routes and trips

gtfs/spec/en/reference.md

@@ -347,10 +347,10 @@ For a given ordered pair of arriving trip and departing trip, the transfer with
 |  ------ | ------ | ------ | ------ |
 |  `from_stop_id` | ID referencing `stops.stop_id` | **Required** | Identifies a stop or station where a connection between routes begins. If this field refers to a station, the transfer rule applies to all its child stops. |
 |  `to_stop_id` | ID referencing `stops.stop_id` | **Required** | Identifies a stop or station where a connection between routes ends. If this field refers to a station, the transfer rule applies to all child stops. |
-| `from_route_id`  | ID referencing `routes.route_id` | Optional | Identifies a route where a connection begins.<br><br>If `from_route_id` is defined, the transfer will apply to the arriving trip on the route for the given `from_stop_id`.<br><br>If both `from_route_id` and `from_trip_id` are defined, `from_trip_id` will take precedence. |
-| `to_route_id`  | ID referencing `routes.route_id` | Optional | Identifies a route where a connection ends.<br><br>If `to_route_id` is defined, the transfer will apply to the departing trip on the route for the given `to_stop_id`.<br><br>If both `to_route_id` and `to_trip_id` are defined, `to_trip_id` will take precedence. |
-| `from_trip_id`  | ID referencing `trips.trip_id` | Optional | Identifies a trip where a connection between routes begins.<br><br>If `from_trip_id` is defined, the transfer will apply to the arriving trip for the given `from_stop_id`.<br><br>If both `from_route_id` and `from_trip_id` are defined, `from_trip_id` will take precedence. |
-| `to_trip_id`  | ID referencing `trips.trip_id` | Optional | Identifies a trip where a connection between routes ends.<br><br>If `to_trip_id` is defined, the transfer will apply to the departing trip for the given `to_stop_id`.<br><br>If both `to_route_id` and `to_trip_id` are defined, `to_trip_id` will take precedence. |
+| `from_route_id`  | ID referencing `routes.route_id` | Optional | Identifies a route where a connection begins.<br><br>If `from_route_id` is defined, the transfer will apply to the arriving trip on the route for the given `from_stop_id`.<br><br>If both `from_trip_id` and `from_route_id` are defined, the `trip_id` must belong to the `route_id`. In this case, `from_trip_id` will take precedence. |
+| `to_route_id`  | ID referencing `routes.route_id` | Optional | Identifies a route where a connection ends.<br><br>If `to_route_id` is defined, the transfer will apply to the departing trip on the route for the given `to_stop_id`.<br><br>If both `to_trip_id` and `to_route_id` are defined, the `trip_id` must belong to the `route_id`. In this case, `to_trip_id` will take precedence. |
+| `from_trip_id`  | ID referencing `trips.trip_id` | Optional | Identifies a trip where a connection between routes begins.<br><br>If `from_trip_id` is defined, the transfer will apply to the arriving trip for the given `from_stop_id`.<br><br>If both `from_trip_id` and `from_route_id` are defined, the `trip_id` must belong to the `route_id`. In this case, `from_trip_id` will take precedence. |
+| `to_trip_id`  | ID referencing `trips.trip_id` | Optional | Identifies a trip where a connection between routes ends.<br><br>If `to_trip_id` is defined, the transfer will apply to the departing trip for the given `to_stop_id`.<br><br>If both `to_trip_id` and `to_route_id` are defined, the `trip_id` must belong to the `route_id`. In this case, `to_trip_id` will take precedence. |
 |  `transfer_type` | Enum | **Required** | Indicates the type of connection for the specified (`from_stop_id`, `to_stop_id`) pair. Valid options are:<br><br> `0` or empty - Recommended transfer point between routes.<br>`1` - Timed transfer point between two routes. The departing vehicle is expected to wait for the arriving one and leave sufficient time for a rider to transfer between routes.<br>`2` - Transfer requires a minimum amount of time between arrival and departure to ensure a connection. The time required to transfer is specified by `min_transfer_time`.<br>`3` - Transfers are not possible between routes at the location. |
 |  `min_transfer_time` | Non-negative integer | Optional | Amount of time, in seconds, that must be available to permit a transfer between routes at the specified stops. The `min_transfer_time` should be sufficient to permit a typical rider to move between the two stops, including buffer time to allow for schedule variance on each route. |