Question:

How do you model a slotted drain (slotted inlet) using InRoads Storm & Sanitary?

Answer:

According to the FHWA Urban Drainage Design Manual, Hydraulic Engineering Circular No. 22 Second Edition (HEC22), Section 4.4.4.3 "Slotted Inlets" states... "Flow interception by slotted inlets and curb-opening inlets is similar in that each is a side weir and flow is subjected to lateral acceleration due to cross slope of the pavement. Analysis of data from the Federal Highway Administration tests of slotted inlets with slot widths >= 45mm (1.75in) indicates that the length of slotted inlet required for total interception can be computed by equation 4-22. Chart 7, is there applicable for both curb-opening and slotted inlets."

Therefore, to model a slotted drain inlet in InRoads S&S, use a Curb Opening Inlet as your structure type.