I remember UK North, they increased service levels September 2006 which ended up causing traffic chaos in Central Manchester, i remember Metrolink Trams getting stuck & delayed because of it, they ended up getting shut down after several accidents, one of them being fatal, the directors were later jailed over unsafe work practices & fraud.
Wilmslow Road corridor in Manchester was ridiculous scene which often saw 5 buses a minute operating up & down that Road, the issue University of Manchester & Owens Park which is the Halls Of Residence is on the same road, so operators were chasing students for passengers, TGFM put a notice up that no buses can start & terminate there, so bus companies operated further up & down the Wilmslow Road than they wanted to, so you had that situation, the Wilmslow Road corridor has calmed down a lot since them days, but still sees buses on high frequencies.
As for the X38, isn't because Arriva got fed up with TrentBarton (TB) often cancelling journeys citing vehicle/staff shortages, so Arriva increased the service to 20 minutes, TB responded by introducing a 15 minute service, & strangely TB can now seemingly operate a full service without cancelling journeys?