Sub-problem 2a: What types of analysis should be conducted on the I-87/Alternate Route 7 interchange?

Step 2. Results

The I-87/Alternate Route 7 interchange is complex. To evaluate the operations of this interchange, we need to break it down into several components, either weaving sections or ramp junctions.

A weaving section is a segment of an uninterrupted flow facility (often a freeway) that requires a high proportion of vehicles to change lanes to reach their desired locations on the freeway. A weaving section is further characterized by the number of lanes in the weaving section, the length of the section, the number of lane changes required of the weaving traffic, and the type of terrain or grade.

A ramp junction is the intersection of an on-ramp or off-ramp with a freeway, a point at which traffic either merges onto the freeway or diverges from the freeway. Similar to a weaving section, there is a higher degree of turbulence in the traffic stream near a ramp than in sections of the freeway that are longer distances away from a ramp or interchange.

While an on-ramp at the beginning of a weaving section or an off-ramp at the end of a weaving section can also be analyzed as a ramp junction, the traffic stream characteristics present in a weaving section are more complex than would be present at a ramp junction alone. Thus, a separate procedure is needed to properly evaluate the effects of this higher degree of turbulence in the traffic stream.