This option controls how downstream structures are numbered for parallel pipes. Within Lucity™, every pipe must be unique in its upstream and downstream structure numbers. To accommodate this, the upstream structure number on multiple pipes must be given a dummy structure number. Within the map, this is accomplished by assigning "indexes" in the i field for pipes that are in parallel. For instance, if you have the above options set, and you have four pipes that are in parallel.
In Lucity, these are the pipes you would have:
Upstream Structure = A-1 Downstream Structure = B-1
Upstream Structure = A-1P2 Downstream Structure = B-1
Upstream Structure = A-1P3 Downstream Structure = B-1
Upstream Structure = A-1P4 Downstream Structure = B-1
Note: We have made the "i" index field for parallel pipes optional; however, it is still required for any clients who have parallel pipes drawn in the map.