الفهرس 
Conventional IntersectionsOnly 14 pages are availabe for public view
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Abstract
The operational performance of signalized intersections can be significantly affected by heavy left-turn movements, and there is a pressing need for more efficient intersection designs due to the increasing wastage of fuel and travel time each year. Traffic engineers have attempted to enhance intersection performance by widening intersection approaches, incorporating protected left-turn signal phases, or even building interchanges. However, these solutions may be impractical or excessively costly. Beyond addressing traffic congestion, conflicts between various road user classes at intersections pose a considerable risk of accidents.
A new method to address the congestion issue is the implementation of unconventional arterial intersection designs (UAIDs). Top of form All UAIDs share the idea of re-routing specific traffic movements from direct through and/or turning movements at intersections. Consequently, unconventional intersections typically have fewer conflict points compared to their conventional counterparts, resulting in a reduced number of signal phases. This in turn improves the traffic operation and safety at intersections compared with conventional intersection designs.
The aim of this research is to assess the operational, environmental, and safety performance of two specific UAIDs: Displaced Left-turn and Parallel Flow Intersection. This study will evaluate them in an isolated manner. The VISSIM v.23 microscopic simulation platform will be employed to test various scenarios, and vehicle trajectory data obtained from VISSIM will be analyzed using the Surrogate Safety Assessment Model (SSAM) to generate conflict results based on indicators such as Time to Collision (TTC) and Post-Encroachment Time (PET).
The Displaced Left-Turn (DLT) intersection eliminates left-turn opposing conflicts by shifting the left-turn lane to the opposing direction and crossing the left-traffic to the left side of the road before the main intersection (Jagannathan and Bared, 2004). Parallel Flow Intersection (PFI) bears some resemblance to the DLT as it eliminates conflicts between left-turning traffic and oncoming through traffic at the primary intersection. However, in the PFI, left-turning traffic from all approaches turn to bypass roadway segments on cross-streets to move parallel, but in the opposite direction, then merge back to the mainline traffic through bypass.
The results showed that the average delays for the PFI were very close to the values obtained for the DLT. Also, DLT and PFI had a higher capacity compared with the conventional intersection. Moreover, the DLT and PFI enhanced the safety conditions relative to the conventional intersection by eliminating all conflicts under all balanced and unbalanced volume levels and reducing the total number of conflicts at most of volume conditions. In addition, the Parallel Flow Intersection and Displaced Left-Turn demonstrated a clear superiority over the conventional intersection in terms of fuel consumption and CO emissions, particularly under high traffic volumes.