Table 1 Traffic light criteria

Green

At least 80% of the target sample size is recruited

At least 65% of the intervention group are achieving Snacktivity™ adherence

At least 60% of the intervention group are achieving physical activity adherence

Attrition < 21%

If all four criteria are met, we will proceed to the full trial with the protocol unchanged (unless there is a clear indication from the qualitative interviews and our experience that would improve the protocol)

Amber

50–79% of the target sample size is recruited

45–64% of the intervention group are achieving Snacktivity™ adherence

45–59% of the intervention group are achieving physical activity adherence

Attrition 21–35%

If one or more of our amber criteria are met, we will plan to adapt the protocol in light of the results of the feedback from the qualitative interviews and our experience to improve which ever criteria are not at the ‘green light’ level before proceeding to the full trial

Red

 < 50% of the target sample size is recruited

 < 45% of the intervention group are achieving Snacktivity™ adherence

 < 45% of the intervention group are achieving physical activity adherence

Attrition > 35%

If one or more of these criteria are met, we would consider the current protocol not feasible and not progress to the phase III RCT with the current protocol