Effects of Safety Facilities on Driver Distance Perception in Expressway Tunnels

Table 4

Distance perception accuracy (α) and device efficiency (β) statistics.

Driver group	N	α		β
		Mean	Standard deviation	Mean	Standard deviation
1 Control Group	30	0.16	0.0903	0.63	0.1322
2 Information Board Group	30	0.09	0.0775	0.78	0.1911
3 Flashing Light Group	30	0.12	0.0955	0.76	0.1710
4 Human-voice Broadcast Group	30	0.25	0.1025	0.52	0.1640
5 Siren Broadcast Group	30	0.13	0.0947	0.73	0.1516