Development of Risk Index of Uninterrupted Traffic Flow According to the Occurrence of Fog

Abstract

The driver's visibility is degraded when weather conditions deteriorate, which affects the traffic flow and induces traffic congestion or accidents. In particular, traffic accidents can be led to chain reaction collisions, with high rate of fatality, when fog occurs in contrast to other weather factors that may restrict visibility. For the development of a traffic risk index, a deviation of the vehicle's speed was set for the traffic risk index by referring to previous study results. In addition, factors that affected the deviation in a vehicle's speed were selected as independent variables based on the traffic flow analysis during occurrences of fog. The visible distance, traffic volume, and speed were selected as the independent variables to estimate the optimal parameters in the regression model. The traffic risk index model during occurrences of fog proposed in this study is an exponential model, with the visible distance and the traffic volume defined as independent variables. According to the study model, traffic risk increased as the visible distance decreased and the traffic volume was lower. Thus, the visible distance that can affect traffic flow during occurrences of fog can be determined in the future based on the results of this study. The study results will be expected to contribute to not only traffic safety improvements, but also the facilitation of traffic flow as drivers and traffic operation managers intuitively recognize the level of risk.

The Pattern of Road Accidents in Fog and the Related Factors in North of Iran in 2014-2018 ​

“…The regression model of deaths due to road accidents in fog at different hours in Guilan between 2014 and 2018 revealed that the mortality rate at 2 AM (IRR = 0.05 and p = 0.005), 9 AM (IRR = 0.06 and p = 0.012), 11 AM (IRR = 0.045 and p = 0.004), 13 (IRR = 0.230 and p = 0.008) and 19 PM (IRR = 0.04 and p = 0.003) were signi cantly lower. Hours 1,3,4,5,6,7,8,10,12,14,15,16,17,18,21,22,23, and 24 could not be investigated due to the incomplete information. Also, the same model indicated a remarkable decrease in the rate of injuries at 2 AM (IRR = 0.2 and p = 0.032), 3 AM (IRR = 0.075 and p = 0.019) and 2 PM (IRR = 0.1 and p = 0.02).…”

“…In another study, the rate of fatality was 6.9% on foggy days which was the highest rate compared with 1.9% on sunny, 2.5% on rainy, and 2.5% on snowy days (7). Furthermore, according to reports, the mortalities due to multi-vehicle chain crash are more likely to occur in foggy and snowy conditions (7), with a risk ratio (RR) of 6 times for rainy, 158 for snowy and 171 for foggy weather (8).…”

“…In China, the analysis of the data from 2005 to 2014 showed that the average nancial cost of RTAs was highest on foggy days compared with that of other bad weather conditions (6). In Korea, the results of the statistical analysis of RTAs in 2014 suggested that 0.5% of all RTAs occurred in foggy weather, which seems to be low compared with the occurrence of accidents on sunny days (80.3%), rainy days (9.6%) and snowy days (1.1%) (7). In another study, the rate of fatality was 6.9% on foggy days which was the highest rate compared with 1.9% on sunny, 2.5% on rainy, and 2.5% on snowy days (7).…”

“…In Korea, the results of the statistical analysis of RTAs in 2014 suggested that 0.5% of all RTAs occurred in foggy weather, which seems to be low compared with the occurrence of accidents on sunny days (80.3%), rainy days (9.6%) and snowy days (1.1%) (7). In another study, the rate of fatality was 6.9% on foggy days which was the highest rate compared with 1.9% on sunny, 2.5% on rainy, and 2.5% on snowy days (7). Furthermore, according to reports, the mortalities due to multi-vehicle chain crash are more likely to occur in foggy and snowy conditions (7), with a risk ratio (RR) of 6 times for rainy, 158 for snowy and 171 for foggy weather (8).…”