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Solution to a capacity problem using non-conventional intersections
Published in Gianluca Dell’Acqua, Fred Wegman, Transport Infrastructure and Systems, 2017
M. Vsetecka, M. Novak, T. Apeltauer
Another example is the multi-level interchange A1 and D549 near Seclin, France (50º32'41’’N 3º3'21’’E), a type of so-called diverging diamond interchange (Maji 2013, Hu 2014, Leong 2015) – left side traffic is used at a short stretch, which creates free left turns and thus increases the capacity and reduces delay time.
Surrogate safety assessment of super DDI design: A case study in Denver, Colorado
Published in Journal of Transportation Safety & Security, 2023
Muhammad Tahmidul Haq, Amirarsalan Mehrara Molan, Khaled Ksaibati
Among the alternative designs, the diverging diamond interchange (DDI), introduced by Chlewicki (2003), attracted the transportation professionals for accommodating higher left-turn volumes and having one less signal phase as compared to CDI. After the first deployment of DDI in Missouri in 2009, close to 100 DDIs have been implemented throughout the nation (ATS/American, 2020). DDI was found to perform very well in terms of traffic operation and safety based on the previous studies (Chlewicki, 2003; Claros, Edara, Sun, & Brown, 2015; Edara, Bared, & Jagannathan, 2005; Hummer et al., 2016; MehraraMolan, 2017; Nye et al., 2019; Walls, Rab, Qi, & R, 2018; Yeom et al., 2015). However, the controversy still remains due to the relative unsatisfying performance of DDI in high through traffic demand and relative dangerous pedestrian crossing for having free-flowing vehicle movements. For instance, a case study in Alabama did not find any specific benefits while replacing CDI with DDI and hence did not recommend DDI as an appropriate candidate for upgrading a conventional diamond interchange (Khan & Anderson, 2016).
Evaluating safety performance of the offset diamond interchange design using VISSIM and surrogate safety assessment model
Published in Journal of Transportation Safety & Security, 2022
Amirarsalan Mehrara Molan, Joseph E. Hummer, Logan J. Aspeitia, Alex S. Deatherage
The DDI design, which was introduced in the US by Chlewicki (Chlewicki, 2003) in 2003, upgrades the performance of conventional diamond interchanges both in terms of the vehicular traffic safety and traffic operation in locations with high left-turning demands. The reason is manily due to the creative concept of the DDI to decrease the number conflict points between vehicle routes, and providing free-flowing left turn movements. However, the DDI has lower capacity with high through traffic demands, and the relatively indirect pedestrian paths through the DDI with free-flow crossings could result in a lower service for pedestrians compared to conventional diamond interchanges (Molan et al., 2019). Based on a recent study (Hunter, Guin, Anderson, & Park, 2019), there is no benefit in upgrading conventional diamond interchanges to a DDI in low left-turning traffic conditions (when the left turn demand is lower than 30% of the total traffic demand). It should be mentioned that pedestrian-activated signals could be considered for the free-flowing crossings; however, pedestrian-activated signals could increase the delay for the traffic movements conflicting pedestrians and would create rear-end vehicular conflicts.
Improving the operational performance of two-quadrant parclo interchanges with median U-turn concept
Published in Transportmetrica B: Transport Dynamics, 2018
Jing Zhao, Wanjing Ma, K. Larry Head, Yin Han
One of the commonly adopted unconventional designs for the interchange is the diverging diamond interchange (DDI), also known as the double crossover diamond interchange (Hu et al. 2014; Yang, Chang, and Rahwanji 2014). The key logic of DDI lies in the fact that the traffic moves to the left side of the roadway between the ramp terminals. The reverse operation of the through traffic between two ramp terminals in a DDI design allows its left-turn traffic flows from the freeway off-ramps to the opposing flows at each sub-intersection (Bared, Edara, and Jagannathan 2005). With such an assignment of flow movements, a DDI design can significantly increase the capacity due to its efficient two-phase signal operation (Tian et al. 2015).