Update reference.md

gtfs/spec/en/reference.md

@@ -196,7 +196,7 @@ File: **Required**
 |  Field Name | Type | Required | Description |
 |  ------ | ------ | ------ | ------ |
 |  `trip_id` | ID referencing `trips.trip_id` | **Required** | Identifies a trip.  |
-|  `arrival_time` | Time | **Conditionally required** | Arrival time at a specific stop for a specific trip on a route. If there are not separate times for arrival and departure at a stop, enter the same value for `arrival_time` and `departure_time`. For times occurring after midnight on the service day, enter the time as a value greater than 24:00:00 in HH:MM:SS local time for the day on which the trip schedule begins.<br/><br/>Scheduled stops where the vehicle strictly adheres to the specified arrival and departure times are timepoints. If this stop is not a timepoint, use leave `arrival_time` empty or provide an interpolated time. Further, indicate that interpolated times are provided with `timepoint`=`0`. If interpolated times are indicated with `timepoint`=`0`, then time points must be indicated with `timepoint`=`1`. Provide arrival times for all stops that are time points. An arrival time must be specified for the first and the last stop in a trip. <br><br> The `arrival_time` field should specify time values whenever possible, including non-binding estimated or interpolated times between timepoints.|
+|  `arrival_time` | Time | **Conditionally required** | Arrival time at a specific stop for a specific trip on a route. If there are not separate times for arrival and departure at a stop, enter the same value for `arrival_time` and `departure_time`. For times occurring after midnight on the service day, enter the time as a value greater than 24:00:00 in HH:MM:SS local time for the day on which the trip schedule begins.<br/><br/>Scheduled stops where the vehicle strictly adheres to the specified arrival and departure times are timepoints. If this stop is not a timepoint, it is recommended to provide an estimated or interpolated time. If this is not available, arrival_time can be left empty. Further, indicate that interpolated times are provided with `timepoint`=`0`. If interpolated times are indicated with `timepoint`=`0`, then time points must be indicated with `timepoint`=`1`. Provide arrival times for all stops that are time points. An arrival time must be specified for the first and the last stop in a trip.|
 |  `departure_time` | Time | **Conditionally required** | Departure time from a specific stop for a specific trip on a route. For times occurring after midnight on the service day, enter the time as a value greater than 24:00:00 in HH:MM:SS local time for the day on which the trip schedule begins. If there are not separate times for arrival and departure at a stop, enter the same value for `arrival_time` and `departure_time`. See the `arrival_time` description for more details about using timepoints correctly. <br><br> The `departure_time` field should specify time values whenever possible, including non-binding estimated or interpolated times between timepoints. |
 |  `stop_id` | ID referencing `stops.stop_id` | **Required** | Identifies the serviced stop. All stops serviced during a trip must have a record in [stop_times.txt](#stop_timestxt). Referenced locations must be stops, not stations or station entrances. A stop may be serviced multiple times in the same trip, and multiple trips and routes may service the same stop. |
 |  `stop_sequence` | Non-negative integer | **Required** | Order of stops for a particular trip. The values must increase along the trip but do not need to be consecutive.<hr>*Example: The first location on the trip could have a `stop_sequence`=`1`, the second location on the trip could have a `stop_sequence`=`23`, the third location could have a `stop_sequence`=`40`, and so on.* |