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Thread: Trip generation for semi-detached houses and duplexes

  1. #1
    Cyburbian nerudite's avatar
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    Trip generation for semi-detached houses and duplexes

    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.

  2. #2
    Cyburbian Rem's avatar
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    We have a rule of thumb standard of 7 per residential unit, regardless of form. There are some more subtle standards available, which tend to be used in traffic studies to support specific applications. In my experience these studies rarely produce results that are materially diffierent from 7 movements per day per residential unit.

    The definitive statndards for Australia and New Zealand are produced by austroads. Their standards are not available on-line - due to the desire of austroads to generate income from their sale. If you can't find another source, maybe you could wade through the austroads site and make a purchase.

  3. #3
    Quote Originally posted by Rem
    We have a rule of thumb standard of 7 per residential unit, regardless of form. There are some more subtle standards available, which tend to be used in traffic studies to support specific applications. In my experience these studies rarely produce results that are materially diffierent from 7 movements per day per residential unit.<snip>
    I'm with Rem, although we use a base of ten trips per day per dwelling unit, regardless of dwelling unit type. The caveat being elderly housing, where we use 4.5 adt.

    I'm interested in knowing more about residential trip generation and will follow this thread for more info.
    Batter up!

  4. #4
    Cyburbian nerudite's avatar
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    I bumping this because I'm desparate!

    The only things I've found so far are from the APA (bizarre, I know) that had a trip generation of 7.0 ADT/duplex unit in their AICP study materials. And also the town of Scarborough, Maine uses 8.0/unit.

    I've decided to be very conservative and go for 8.5 ADT/unit as the proposed duplex units will be only slightly smaller than a typical single family detached dwelling.

  5. #5
    maudit anglais
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    Sorry Nerudite, I didn't see this thread before.

    In my experience, semi-detached houses have the same trip-making characteristics as detached housing. A duplex - which here means an apartment within a house form building (e.g. 1 house, 1 lot, two dwelling units) is slightly different as the second unit is almost always a rental unit.

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