Interrupted time-series regression with ARIMA errors for (a) all accidents and (b) serious and fatal accidents only, by study area
| Parameter | Estimate (95% CI) | p Value | Parameter | Estimate (95% CI) | p Value | ||
|---|---|---|---|---|---|---|---|
| Study area | Series | (a) All accidents | (b) Serious and fatal accidents only | ||||
| Glasgow and surrounding local authorities | Change in series for full study period | Log ar(7 9 10 12) sarima(0,1,0,12) | −0.042 | <0.0001 | Log ar(1 7 12) sarima(0,1,0,12) | −0.074 | <0.0001 |
| (−0.054 to −0.030) | (−0.107 to −0.041) | ||||||
| Change in series during M74 construction period | −0.066 | <0.0001 | 0.046 | 0.337 | |||
| (−0.098 to −0.035) | (−0.048 to 0.139) | ||||||
| Change in series following opening of M74 motorway extension | −0.001 | 0.295 | 0.0027 | 0.385 | |||
| (−0.003 to 0.001) | (−0.003 to 0.009) | ||||||
| Intervention area (South, M74 extension) | Change in series for full study period | Log ar(1 12 13) sarima(0,1,0,12) | −0.41 | 0.003 | Log ma(1 12) sarima(0,1,0,12) | −0.088 | <0.0001 |
| (−0.069 to −0.014) | (−0.125 to −0.063) | ||||||
| Change in series during M74 construction period | −0.026 | 0.558 | −0.082 | 0.705 | |||
| (−0.116 to 0.063) | (−0.451 to 0.299) | ||||||
| Change in series following opening of M74 motorway extension | −0.001 | 0.951 | −0.003 | 0.67 | |||
| (−0.006 to 0.006) | (−0.017 to 0.011) | ||||||
| Comparator area (East, M8 motorway) | Change in series for full study period | Log ar(1 12) sarima(0,1,0,12) | −0.053 | 0.001 | Log ma(12) sarima(0,1,0,12) | −0.119 | <0.0001 |
| (−0.083 to −0.022) | (−0.163 to −0.075) | ||||||
| Change in series during M74 construction period | 0.065 | 0.264 | −0.044 | 0.831 | |||
| (−0.049 to 0.179) | (−0.446 to 0.358) | ||||||
| Change in series following opening of M74 motorway extension | 0.005 | 0.142 | 0.012 | 0.255 | |||
| (−0.002 to 0.013) | (−0.008 to 0.032) | ||||||
| Control area (North) | Change in series for full study period | Log ar(11) sarima(0,1,1,12) | −0.054 | 0.002 | Log ma(12) sarima(0,1,0,12) | −0.074 | <0.0001 |
| (−0.088 to −0.019) | (−0.115 to −0.033) | ||||||
| Change in series during M74 construction period | −0.353 | 0.029 | −0.08 | 0.722 | |||
| (−0.669 to −0.037) | (−0.521 to 0.361) | ||||||
| Change in series following opening of M74 motorway extension | −0.029 | <0.0001 | 0.0001 | 0.994 | |||
| (−0.043 to −0.016) | (−0.024 to 0.024) | ||||||
ARIMA, autoregressive integrated moving average.