  Alternative intersection designs (AIDs) can improve the performance of an
intersection by not only reducing the number of signal phases but also change
the configuration of the conflicting points by re-routing traffic. However the
AID studies have rarely been extended to Connected and Automated Vehicle (CAV)
which is expected to revolutionize our transportation system. In this study, we
investigate the potential benefits of CAV to two AIDs: the diverging diamond
interchange (DDI) and the restricted crossing U-turn intersection. The
potential enhancements of AID, CAV, and the combination of both are quantified
via microscopic traffic simulation. We found that CAV is able to positively
contribute to the performance of an intersection. However, converting an
existing conventional diamond interchange (CDI) to a diverging one is a more
effective way according to the simulation results. DDI improves the throughput
of a CDI by 950 vehicles per hour, a near 20% improvement; whereas with full
penetration of CAV, the throughput of a CDI is increased only by 300 vehicles
per hour. A similar trend is observed in the average delay per vehicle as well.
Furthermore, we assess the impact for the driver's confusion, a concern for
deploying AIDs, on the traffic flow. According to the ANOVA test, the negative
impacts of driver's confusion are of statistical significance.
