Table 2

ARIMA time series intervention models for killed, serious injuries and case-fatality rates (CFRs) between 1988–1999. On November 1993 the legal speed limit was changed from 90 kph to 100 kph

Road Type	Variable	Model*	Parameter (Lag)†	Parameter Estimate	t-value‡
*Models: Intervention models involving a step function were observed for all models. There was no evidence within any of the models to support a significant pulse function or decay effect.
†INTV: Intervention occurred on November 1993 when the speed limit was legally raised from 90 kph to 100 kph
‡The significance levels for the T-values is as follows: 1.977, p = 0.05; 2.353, p = 0.02; 2.611, p = 0.01; 3.361, p = 0.001.
§CFRS is the modified case fatality rate calculated as follows deaths/(deaths+serious injuries)
All Roads Combined	Killed	(0,0,0)(0,1,1)s	MA(12)	0.879	7.11
			INTV	4.694	3.94
	Serious Injuries	(0,1,1)(1,0,0)s	MA(1)	0.593	8.63
			AR(12)	0.309	3.68
			INTV	−31.7	−1.24
	CFR	(1,0,1)	AR(1)	0.993	327.6
			MA(1)	1.017	69.62
			INTV	0.393	4.54
	CFRS§	(1,0,0)	AR(1)	0.242	2.967
			INTV	2.502	6.048
Urban Roads	Killed	(0,0,0)	INTV	1.625	2.129
	Serious Injuries	(0,1,1)(1,0,0)s	MA(1)	0.75	13.24
			AR(12)	0.3	3.6
			INTV	−3.31	−0.29
	CFR	(1,0,1)	AR(1)	0.918	37.29
			MA(1)	0.805	14.53
			INTV	−0.075	0.724
	CFRS§	(1,0,1)	AR(1)	0.614	3.24
			MA(1)	0.515	2.409
			INTV	1.522	3.288
Interurban Roads	Killed	(0,0,0)(0,1,1)s	MA(12)	0.886	6.815
			INTV	3.11	3.172
	Serious Injuries	(0,1,1)(1,0,0)s	MA(1)	0.472	6.29
			AR(12)	0.304	3.63
			INTV	−33.92	−1.74
	CFR	(1,0,1)	AR(1)	0.986	54.04
			MA(1)	0.725	10.92
			INTV	1.275	2.578
	CFRS§	(1,0,0)(1,0,0)s	AR(1)	−0.336	2.84
			AR(12)	0.44	3.899
			INTV	4.12	2.611