Table 1. Details of the four hypothesis tests carried out to assess if the occurrence of hydroplaning and high-risk events increase the risk of fatal accidents.

MTD = 0.04 inch	Total Count	N1	N2	x	y	P1	P2	Z score	P
p1 = The proportion of fatal accidents for vehicles travelling within the speed limit under conditions conducive for HP	218598	1532	217066	1099	131840	0.72	0.61	8.79	< 0.05
p2 = The proportion of fatal accidents for vehicles travelling within the speed limit under conditions NOT conducive for HP
H0: p1 < = p2
H1: p1 > p2
p1 = The proportion of fatal accidents for vehicles travelling within the speed limit during rainfall under conditions conducive for HP	60731	1532	59199	1099	38006	0.72	0.64	6.08	< 0.05
p2 = The proportion of fatal accidents for vehicles travelling within the speed limit during rainfall under conditions NOT conducive for HP
H0: p1 < = p2
H1: p1 > p2
p1 = The proportion of fatal accidents for vehicles travelling within the speed limit when HPS < = SL.	218598	27	218571	21	132918	0.78	0.61	1.81	< 0.05
p2 = The proportion of fatal accidents for vehicles travelling within the speed limit when HPS > SL OR NO HP.
H0: p1 < = p2
H1: p1 > p2
p1 = For HP events, the proportion of fatal accidents for vehicles travelling within the speed limit, when HPS < = SL	1532	27	1505	21	39	0.78	0.03	19.96	< 0.05
p2 = For HP events, the proportion of fatal accidents for vehicles travelling within the speed limit, when HPS > SL
H0: p1 < = p2
H1: p1 > p2
MTD = 0.004 inch	Total Count	N1	N2	x	y	P1	P2	Z score	P
p1 = The proportion of fatal accidents for vehicles travelling within the speed limit under conditions conducive for HP	218598	35544	183054	23264	109675	0.65	0.60	19.57	< 0.05
p2 = The proportion of fatal accidents for vehicles travelling within the speed limit under conditions NOT conducive for HP
H0: p1 < = p2
H1: p1 > p2
p1 = The proportion of fatal accidents for vehicles travelling within the speed limit during rainfall under conditions conducive for HP	60731	35544	25187	23264	15841	0.65	0.63	6.49	< 0.05
p2 = The proportion of fatal accidents for vehicles travelling within the speed limit during rainfall under conditions NOT conducive for HP
H0: p1 < = p2
H1: p1 > p2
p1 = The proportion of fatal accidents for vehicles travelling within the speed limit when HPS < = SL.	218598	284	218314	234	132705	0.82	0.61	7.45	< 0.05
p2 = The proportion of fatal accidents for vehicles travelling within the speed limit when HPS > SL OR NO HP.
H0: p1 < = p2
H1: p1 > p2
p1 = For HP events, the proportion of fatal accidents for vehicles travelling within the speed limit, when HPS < = SL	35544	284	35260	214	1145	0.75	0.03	63.11	< 0.05
p2 = For HP events, the proportion of fatal accidents for vehicles travelling within the speed limit, when HPS > SL
H0: p1 < = p2
H1: p1 > p2