The intended meaning of an empty stop_times.timepoint value may be unclear. Quoted below from trips.txt. See, in particular, statements that are somewhat at odds with each other in bold italic below.

Field Name	Required	Details
timepoint	Optional	The timepoint field can be used to indicate if the specified arrival and departure times for a stop are strictly adhered to by the transit vehicle or if they are instead approximate and/or interpolated times. The field allows a GTFS producer to provide interpolated stop times that potentially incorporate local knowledge, but still indicate if the times are approximate. For stop-time entries with specified arrival and departure times, valid values for this field are:
		* empty - Times are considered exact.
		* 0 - Times are considered approximate.
		* 1 - Times are considered exact.
		For stop-time entries without specified arrival and departure times, feed consumers must interpolate arrival and departure times. Feed producers may optionally indicate that such an entry is not a timepoint (value=0) but it is an error to mark a entry as a timepoint (value=1) without specifying arrival and departure times.

If there are no times provided and stop_times.timepoint is empty, then should feed consumers therefore assume that times should be interpolated? Is there any way of indicating times should not be interpolated, and would that ever be necessary?