“…ese two categories include the real-accident data analyzing and the simulation-based safety study. In the real-accident studies, the effect of some factors (such as mainline speed at the beginning of the weaving segments, the speed difference between the beginning and the end of the weaving segment, the logarithm of the volume, the maximum length of the weaving area [1], the heavy vehicle rate, the hourly traffic volume, the speed differential between cars and heavy vehicles, the number of accesses [2], the number of vehicles that enter and exit the freeway at a specific segment, the length of the speed change lane, the speed of off-ramps [3], parallel-type or taper-type exit ramps [4], left-side or right-side merging and diverging areas [5,6], the number of lanes on freeways, the number of lanes on ramps, and the speeding-related crashes [7]) on the number and/or severity of accidents was separately investigated and some models were developed. When there are no registered data about the accidents in a specific facility or when someone is trying to design that facility or when the facility has not yet been built, simulation-based safety studies/estimations such as conflict analysis by microscopic simulation and surrogate safety measures (SSMs) including time-to-collision (TTC), postencroachment time (PET), proportion of stopping distance (PSD), crash potential index (CPI), unsafe density (UD), max speed (Max S), relative speed (ΔV), kinetic energy (KE), and deceleration rate to avoid collision (DRAC) are often used to estimate the danger or risk of possible collisions.…”