Table 1

Interrupted time-series regression with ARIMA errors for (a) all accidents and (b) serious and fatal accidents only, by study area

ParameterEstimate (95% CI)p ValueParameterEstimate (95% CI)p Value
Study areaSeries(a) All accidents(b) Serious and fatal accidents only
Glasgow and surrounding local authoritiesChange in series for full study periodLog ar(7 9 10 12) sarima(0,1,0,12)−0.042<0.0001Log 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<0.00010.0460.337
(−0.098 to −0.035)(−0.048 to 0.139)
Change in series following opening of M74 motorway extension−0.0010.2950.00270.385
(−0.003 to 0.001)(−0.003 to 0.009)
Intervention area (South, M74 extension)Change in series for full study periodLog ar(1 12 13) sarima(0,1,0,12)−0.410.003Log 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−0.0260.558−0.0820.705
(−0.116 to 0.063)(−0.451 to 0.299)
Change in series following opening of M74 motorway extension−0.0010.951−0.0030.67
(−0.006 to 0.006)(−0.017 to 0.011)
Comparator area (East, M8 motorway)Change in series for full study periodLog ar(1 12) sarima(0,1,0,12)−0.0530.001Log 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 period0.0650.264−0.0440.831
(−0.049 to 0.179)(−0.446 to 0.358)
Change in series following opening of M74 motorway extension0.0050.1420.0120.255
(−0.002 to 0.013)(−0.008 to 0.032)
Control area (North)Change in series for full study periodLog ar(11) sarima(0,1,1,12)−0.0540.002Log 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−0.3530.029−0.080.722
(−0.669 to −0.037)(−0.521 to 0.361)
Change in series following opening of M74 motorway extension−0.029<0.00010.00010.994
(−0.043 to −0.016)(−0.024 to 0.024)
  • ARIMA, autoregressive integrated moving average.