Table 4 - Visibility in Snow vs. Snowfall Intensity Chart1

(For Sample Questions Only)

TABLE 4 - VISIBILITY IN SNOW VS. SNOWFALL INTENSITY CHART1

Lighting Temperature Range Visibility in Snow (Statute Miles)
ºC ºF Heavy Moderate Light Very Light
Darkness -1 and above 30 and above = 1 > 1 to 2½ > 2½ to 4 > 4
Below -1 Below 30 = 3/4 > 3/4 to 1½ > 1½ to 3 > 3
Daylight -1 and above 30 and above = ½ > ½ to 1½ > 1½ to 3 > 3
Below -1 Below 30 = 3/8 > 3/8 to 7/8 > 7/8 to 2 > 2

1  Based on:  Relationship between Visibility and Snowfall Intensity (TP 14151E), Transportation Development Centre, Transport Canada, to be published in November 2003; and Theoretical Considerations in the Estimation of Snowfall Rate Using Visibility (TP 12893E), Transportation Development Centre, Transport Canada, November 1998. HOW TO READ THE TABLE Assume that the daytime visibility in snowfall is 1 statute mile and the temperature is -7°C. Based on these conditions, the snowfall intensity is light. This snowfall intensity is used to determine which holdover time guideline value is appropriate for the fluid in use.