SWMM - Undersized culverts

[MOEngr]

We are using the SWMM model (Version 5) to complete a neighborhood stormwater study (total watershed Area about 85 acres). We are trying to create an exisitng conditons model using SWMM (Requirement per our client). How do you exactly model an undersized culvert under a road within SWMM? We have it as a conduit with a Juntions on both ends. We are also using the OVERFLOW option as a flow divider. Also we are using Dynamic Wave Routing.