Modeling safety and traffic operations at freeway weaving sections

Freeway conflicts are potential crashes. It is hypothesized that conflicts can be used as an indicator of freeway safety and that minimizing the potentiality of freeway collisions will minimize crash occurrence and crash severity, especially freeway weaving section crashes. The benefits to the individual and society through this reduction in the potentiality for vehicular crashes are many, such as: the preservation of human life and lessening trauma, more efficient traffic operations in the facility, and the direct promotion of the individual's mobility and safety on the freeway system.;A Spearman's correlation coefficient of +0.74 existed between lane change conflict rates and reported angle/sideswipe crash rates and +0.95 between rear-end conflict rates and rear-end crash rates for the eight ramp weaves that had moderate lengths between 850 and 1,000 feet. The hypothesis could not be rejected at a 97.5% confidence level at moderate lengths, i.e., there are positive correlations between the conflict rates and their respective crash rates. For the ten sites with short lengths between 500 and 650 feet, the hypothesis tests indicated no correlations between the conflict and accident rates at a level of significance of 2.5%;The model was able to identify that the two sites with 2,000 feet lengths and the highest weaving volumes had the highest average lane change and rear-end conflict rates even though the corresponding crash rates were not significantly higher than the moderate length sites. These two sites have been targeted by the Illinois State Toll Highway Authority for reconstruction because of their known history of generating severe traffic turbulence and hazardous driving maneuvers. Thus, using conflict rates as an indicator of safety in ramp weaves proved to be a better indicator than the use of crash rates.;In terms of operations in freeway weaving sections, conflict rates were shown to be better measures of effectiveness than the present weaving and nonweaving speed measures and shown to be adequate microscopic measures of turbulence. The difference between average space mean weaving and nonweaving speeds on the other hand is a good macroscopic measure. Total conflicts are shown to be a consistent indicator of weaving level-of-service.