Sub-problem 3b: Ramps

Sometimes the configuration of the ramps is simple, as might be the case at a standard diamond or cloverleaf interchange. In a cloverleaf, for example, you’d typically have four diverges where the right-hand ramps start, four merges where they end, and four weaving sections between the merge and diverge points for the left-hand loop ramps. Hence, your set of ramp analyses for the interchange would involve twelve studies: four analyses for the merges; four for the diverges; and four for the weaving sections.

In the interchange at I-787, the ramps are interlaced and a collector-distributor provides the starting and ending points for three ramps. A vehicle traveling westbound on Route 7 encounters the diverge of the left-hand and right-hand ramps to I-787, which split shortly thereafter. The vehicle then has a merge with the loop ramp from I-787 north and the merge with the ramp from I-787 south. Traveling east on Route 7, there is the diverge of the collector-distributor road and then its merge back into the mainline. The collector-distributor provides the starting point for the right-hand ramp to I-787 south, the merge with the loop ramp from I-787 south, and the starting point for the loop ramp to I-787 north. At the end is the merge with the right hand ramp from I-787 north. The right-hand ramp leading from Route 7 east to I-787, once it diverges from the collector-distributor road, merges with the semi-direct ramp coming from Route 7 west merging with I-787 south.

In this sub-problem, we’re going to do a capacity analysis on the roadways that make up the ramps and two merge analyses. These two analyses demonstrate how to study the ramps at an interchange.