It was also determined that the SPUI had more sideswipe accidents than partial cloverleafs or diamond interchanges. In these cases, an unsignalized system can be used to minimize delay. The SPUI has a consistently lower delay than the diamond for all volume scenarios tested. The SPUI can operate at LOS D or better at entering volume of 5500 vph or less. The diamond can operate at LOS D or better until an entering volume of 4500 vph.
Signalized delay is increased at the SPUI when the left turns off the ramps are unbalanced.
There is also some indication that unbalanced mainline lefts also result in increased delays. This indicates that full cloverleafs and partial cloverleafs are not suitable for roads with large weaving volumes. Partial cloverleafs have a superior signalized LOS to the SPUI and diamond at all entering volumes that were studied, since large left-turning movements are handled by loop ramps. Based on the information obtained in this study, it is possible to identify several factors that affect what type of interchange should be used in a given situation. The survey results helped to further validate the information found in the literature review, and also influenced the formulation of the guidelines.