Street Mutation

Street Mutation

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Perfectly aligned streets of standard widths can be rigid and lifeless. But incremental variations to street alignment and width can result in unforeseen problems.

One model of development is for streets to be laid out in perfect alignment, with plots neatly facing them.  But there are many other possible forms of street and plot relationship, as history has shown – and many of the most successful grew (or changed) incrementally, without being planned in advance as they ended up.  How can we incorporate such a process today?

One problem is procedural.  How can such a process occur within the standard platting process that exists in many locations?  We have found a relatively simple mechanism, which addresses both street mutations and other sequential adaptations.  It creates a series of “dummy lots” within a standard platting process (see example at left) and then allows owners to make sequential modifications to them, using a simple process known as “lot line adjustment.”  The most difficult part of the process is the treatment of the right-of-way, which is typically “dedicated” to the City or other jurisdiction within the platting process.  Again, this can be done as a standard or “dummy” tract, and then adjusted through the lot line process.

This requires that the City or other street authority establish very minimum standards for street width, curb design, sidewalk and streetscape elements, and so on.  (These can also be expressed as patterns.)  In a low-speed, relatively low-volume condition, such standards can be very loose.  (See e.g. the work of Hans Monderman and other researchers in the field of so-called “shared space” design.)

Once the standards are established, then the owners are allowed to make their street mutations as they choose, within the minimum standards.  The local authority over the streets will review and approve the plans, or else advise of changes needed.

The only other element that is essential is that each successive owner must connect to the end-points established by the previous owner, and do so without exceeding the geometric standards specified by the local authority.  The owners may wish to work together to create a shared pattern such as a front courtyard, garden or parking area.


Where street mutations are desired within a local development area, create a standard or “dummy” street tract, and then specify a nominal, minimum and maximum width.  Then each successive owner may establish their own frontage property line, following the simple rule:  connect to the previous adjacent owner’s frontage property line, stay within the minimum and maximum widths, use the established curb pattern(s) for that area, and integrate other approved design elements into the streetscape.

If adjoining owners wish, they can create Attached Buildings.  They can also make agreements to share features, such as Front Garden,  Entrance Square, Shared Parking, Close…etc

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