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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