Mixed method matrix summary of evidence strength grades according to barrier within each of the 3 delays.

Barriers are in order of evidence strength. Not all study methods could, by design, evidence all the delays (labelled as Not Applicable). Barriers for which a study methodology provided no evidence were categorised as silent. This silence could be a limitation of a method being unsuitable to detect evidence for a barrier, or suggestive that the barrier does not exist. A traffic light colour code, green for strong, amber for moderate, and red for weak has been used to facilitate interpretation.