Only in Cambridge…

… would buses run less frequently during peak times. From University Estate Management:

The published service frequency will change from 15 minutes to 20 minutes during peak hours (07.00-09.00 and from 16.00). The published off-peak service frequency will remain 15 minutes.

It seems slightly less insane if you consider that “peak times” is referring to traffic levels in Cambridge rather than bus usage, which being a University service is unlikely to coincide with the normal rush hour. Indeed the email goes on to say:

The revised timetable better reflects achievable bus travel times during peak hours and should result in a more reliable service.