After having finalized the designs for all viable alternatives, the team needed an unbiased form of selecting which was the most viable alternative. Thus, the team used Caltran’s project development team’s Weighted Decision Matrix. This matrix would be made up of different factors that were important to the designs. Each factor was included because of their importance to the project and were given an appropriate weight based on their importance. 

 

As seen from the chart below, there are varying degrees of weights depending on the factor. Local circulation is a major factor as two of the project's needs was to alleviate congestion and to provide more mobility to the users. Thus, this factor deserved a weight of 10. Freeway Impact is just as crucial as there would be little benefit to a project that had negative results on existing conditions. Therefore, it was assigned a weight of 9. Driver and Pedestrian User Experience is also important as some interchange layouts are foreign to some and a familiar layout is more comfortable for users. Thus, a weight of 8 and 7 were assigned respectively. Emergency Vehicles is ranked fairly high as well due to the fact that the interchanges provide different expectations for emergency vehicles. As users during an emergency may not be familiar with a layout, it may impact their driving ability. In addition to these major factors, some minor factors were also addressed including the constructability and adaptability of an interchange. Though these minor qualities are still important to the design, they are not the primary reasons to consider building an alternative; these minor factors were assigned a weight of 3 and 1.

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After having decided on the weight of each factor, each alternative was given a rank from 1 to 10 that was agreed upon by every single member of the team. These ranks were then multiplied by the weight for a score. At  the end, each score was summed up and we end up with a final score for each alternative, as shown in the chart below.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Our final decision was ultimately the Hybrid Diamond with a final score of 463 compared to SPUI’s 368 and Roundabout’s 380. The team is very confident in this choice as it answers all our purpose and needs, works the best within right of way constrictions, and provides the most comfortable experience for users.