Improving accuracy of shape_dist_traveled


I’ve recently noticed that the shape_dist_traveled fields in realtime bus GTFS bundle (both shapes.txt and stop_times.txt) significantly deviates over the course of the route.

I think it may have something to do with the change in June when the TSN was removed from the shape.

As an example, I compared the shape_dist_traveled field for shape_id 177 with the cumulative distance travelled calculated using the WGS84 coordinates provided. The shape_dist_traveled field is always larger – I get a deviation of over 300 meters at the end of the route.

It would be great if data can be better aligned!