-ve stops per week

[mem48]

I'm getting -ve values for the number of stops per week.

The problem is that sometimes calendar_dates include an exclusion for a day the bus doesn't run. e.g. Bus runs Monday to Friday but the date excluded is a Saturday.

I think this happens because exclusions in CIF are given as date ranges, but are then converted to single dates for GTFS.

The problem is then that cancelling a non-existent bus reduced the service for another time that the bus did run.

Needs fixing at conversion by removing inappropriate exclusions.