Well, I just received (after several months of waiting!) the ITE Trip Generation Manual (7th Edition). With all of the changes they have made to include so many different types of specialized commercial uses and retirement home categories, I was a little dismayed to find that they do not have a separate land use category for duplexes or semi-detached (single family attached) uses.
I am analyzing a redistricting (rezoning) application that is proposing to go from typical single family detached units to attached dwelling on smaller lots. I would assume that there would be a slightly lower ADT figure per unit for the attached units, but I can't find any source materials. A recent study provided to me for this area assumed that the duplexes would be similar to townhouses (a 6.5 +/- ADT per unit), which seems too low.
Anyone know of a good source for trip generation rates on various types of residential uses other than ITE? As for context, the city I work for is suburban in nature and is considered a bedroom community. The city is fairly dense for a suburb with good transit ridership.