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Table 6 Speed (mean values in km/h) and standard deviation (SD) for roads with and without road lighting in different weather conditions (clear, rain, snow), and natural light conditions (darkness, twilight, daylight)

From: Effects of weather conditions, light conditions, and road lighting on vehicle speed

Weather condition

No road lighting (n = 8)

Road lighting (n = 17)

Mean

SD

Mean

SD

Clear

 Darkness

93.0

18.8

63.7

18.5

 Twilight

91.7

19.8

63.0

19.5

 Daylight

90.9

19.1

65.2

20.6

Rain

 Darkness

91.8

18.6

66.7

20.7

 Twilight

90.2

20.9

67.9

21.7

 Daylight

90.4

18.8

67.7

22.1

Snow

 Darkness

83.2

16.2

58.7

13.5

 Twilight

86.4

18.9

55.4

12.0

 Daylight

87.8

17.5

59.0

15.0