Table 3 Summary table on risk of bias of the included interrupted time series studies (excludes two studies (35, 36) that could not be assessed)
ITS | Intervention independent of other changes | Shape of the intervention effect pre-specified | Intervention unlikely to affect data collection | Knowledge of the allocated interventions adequately prevented during the study | Incomplete outcome data adequately addressed | Study free from selective outcome reporting | Study free from other risks of bias |
|---|---|---|---|---|---|---|---|
Whittam 2006 [18] | Low risk (ARIMA model used and had comparator site) | Low risk | Low risk | Low risk | Low risk | High risk (crash data only for 16–19 year olds) | Low risk (has comparator site, using ARIMA model) |
Good quality study | |||||||
Murry 1993 [19] | Low risk (authors state that data were transformed to isolate the experimental effect from any extraneous influences) | Low risk | Low risk | Low risk | Low risk | High risk (using proxy indicator, using certain age group only) | Low risk (using comparator site, using model) |
Good quality study | |||||||
Newstead 1995 [20] | Low risk (regression model used to account for other factors) | Low risk | Low risk | Low risk | Low risk | Unclear risk (using proxy indicator) | Low risk (using regression model, but no comparator site) |
Good quality study | |||||||
Tay 2002 [21] | Low risk (used regression models to exclude other factors) | Low risk | Low risk | Low risk | Unclear risk (States that some inconsistencies may exist in the reporting as done by local police) | Unclear risk (used proxy measures) | Low risk |
Good quality study | |||||||
Fell 2008 [23] | High risk (other enforcement measures took place) | Low risk | Low risk | Low risk | Low risk | Low risk | Low risk |
Intermediate quality study | |||||||
Zwicker 2007a [24] | High risk (enforcement also took place) | Low risk | Low risk | Low risk | Low risk | Low risk | Low risk (used ARIMA model and applied parameters to model periodic fluctuations in the crash rates) |
Intermediate quality study | |||||||
Zwicker 2007b [25] | High risk (enforcement also took place) | Low risk | Low risk | Low risk | Low risk | Low risk | Low risk (contiguous county data were used to remove factors that may have obscured the effect of the campaign on the trend) |
Intermediate quality study | |||||||
Lacey 2008 [26] | High risk (law enforcement activities also took place) | Low risk | Low risk | Low risk | Low risk | Low risk | Low risk (ARIMA model used) |
Intermediate quality study | |||||||
Epperlein 1987 [29] | Unclear risk (no comparator site, but daytime crashes used to account for other changes) | Low risk | Low risk | Low risk | Low risk | Unclear risk (using proxy indicator) | High risk, not using model |
Low quality | |||||||
Miller 2004 [30] | High risk (media campaign done together with other enforcements, though model was used to look at each interventions) | Low risk | Low risk | Low risk | Low risk | Unclear risk (using proxy indicator, fatal nighttime crashes) | High risk (ARIMA model was used, but evaluation of mixed approaches in different areas over different period) |
Low quality study | |||||||
Agent 2002 [27] | High risk (enforcement activities also took place as part of the campaign) | Low risk | Low risk | Low risk | Low risk | Unclear risk (documentation of alcohol use is dependent on the reporting officer) | High risk (no model used) |
Low quality study | |||||||
Solomon 2008 [28] | High risk (enforcement measures also in place) | Low risk | Low risk | Low risk | Low risk | Low risk | High risk (Only looking at changes in absolute numbers, no application of models, no comparator site) |
Low quality study | |||||||
Beck 2009 [31] | High risk (enforcement also took place) | High risk (point of analysis not clear) | Low risk | Low risk | Low risk | Low risk | High risk (only looking at the absolute number of alcohol-related crashes, not using any models or accounting for rates in comparator sites) |
Low quality study | |||||||
NHTSA 2007 [32] | High risk (enforcement also took place) | Low risk | Low risk | Low risk | Low risk | Low risk | High risk (compared with non-intervention sites, but no model used. Unclear if other factors accounted for) |
Low quality study | |||||||
Suriyawongpaisal 2002 [33] | High risk (enforcement measures also used) | High risk (point of analysis is not the point of intervention, and not clearly stated why the data points were selected) | Low risk | High risk (hospital staff of the study sites were not blinded, and could have affected how they collected data) | High risk (not sure what proportion of cases were missed in each period, data collection dependent on hospitals enrolled) | Unclear risk | High risk (the study did not account for other changes that could have affected the outcome) |
Low quality study |