45 Minute Gaps in a Half Hourly Frequency

In recent years, Stagecoach putting sporadic 15 minute gaps in a 10 minute frequency, or 30 minute gaps in a 20 minute frequency Monday to Friday daytimes has become a feature of some timetables in Hull. Presumably this cuts the vehicle requirement down by one and saves a driver or two whilst just about maintaining 'headline' frequencies? 

Stagecoach took things one stage further in their 31st August service changes - 45 minute gaps in otherwise half hourly services on routes 4 to Orchard Park and the 6 to Kingswood. To provide an example, from Orchard Park Tesco the 4 departs at 0900, 0930, 1000 then 1045, half hourly to 1315, then 1400. Again these apply Monday to Friday only - the 4 remains a consistent half hourly frequency on both Saturday and Sunday daytimes, as does the 6 on Saturday daytimes.