Modeling safety performance of the new super DDI design in terms of vehicular traffic and pedestrian

Publication date: June 2019Source: Accident Analysis & Prevention, Volume 127Author(s): Amirarsalan Mehrara Molan, Joseph E. Hummer, Khaled KsaibatiAbstractMost existing interchanges in the United States were built more than 50 years ago based on old design policies. Many of these designs are not consistent with current traffic and pedestrian demands anymore. Therefore, this inconsistency has caused problems regarding operation and safety. This paper models safety performance of a new design called super diverging diamond interchange (super DDI) considering VISSIM simulation and surrogate safety assessment model (SSAM). Six other interchange designs were also considered for comparing to the new super DDI design. Overall, 252 simulation scenarios were modeled in VISSIM and then tested by SSAM. Also, the same number of tests were considered to evaluate pedestrian performance of the designs considered in this study. Based on results, super DDI showed a high potential either in terms of traffic safety and pedestrian safety. In comparison to other designs, super DDI had the minimum number of simulated conflicts as well as the lowest mean speed and time to collision (TTC) of simulated conflicts. This fact shows that super DDI could perform promising in reducing crash frequency and crash severity. Reviewing the geometry of the super DDI, lower traffic involving in each conflict point should be one of the main reasons for the promising traffic safety performance of the design. Regard...
Source: Accident Analysis and Prevention - Category: Accident Prevention Source Type: research