Low Visibility Occurrence Risk Index (LVORI)
The Low Visibility Occurrence Risk Index (LVORI) was developed based on Florida automobile accident reports when fog/smoke was a factor, and the associated weather (Lavdas and Achtemeier, 1995). It is an index for probability of low visibility, and ranges from 1 - 10, depending on relative humidity and smoke dispersion index. A 1 means there is almost no chance of low visibility, while a 10 indicates low visibility is likely. This Index is a function of relative humidity and smoke dispersion index.
From operational experience, one should be VERY CAUTIOUS ABOUT BURNING if one of the following situations occurs:
- When LVORI for a nighttime forecast period is 8,9 or 10
- When ACTIVE SMOKE from stumps logs, etc. is present during the night
- When there is a roadway within three miles of a burn site with open fields, logging roads, or open streams that can provide an easy transit of the smoke from the burn site to the roadway
Although not as dangerous as an index value from 8 to 10, LVORI of 6 or 7 should be treated with caution if there is active smoke produced during the night, and the burn site is near a roadway.
LVORI Category | Interpretation |
---|---|
1 | Lowest proportion of accidents with smoke and/or fog reported (130 of 127,604 accidents, or just over 0.0010 accidents.) |
2 | Physical or statistical reasons for not including in category 1, but proportion of accidents not significantly higher. |
3 | Higher proportion of accidents than category 1, by about 30% to 50%, but of marginal significance (1%-5%). |
4 | Significantly higher than category 1, by a factor of 2. |
5 | Significantly higher than category 1, by a factor of 3 to 10. |
6 | Significantly higher than category 1, by a factor of 10 to 20. |
7 | Significantly higher than category 1, by a factor of 20 to 40. |
8 | Significantly higher than category 1, by a factor of 40 to 75. |
9 | Significantly higher than category 1, by a factor of 75 to 125. |
10 | Significantly higher than category 1, by a factor of 150. |