A primary purpose of resilient planning is to prepare communities for economic downturns such as recessions and reductions in base employment.  Resilient communities tend to cluster the built environment to minimize travel and its costs.  The foundation for such physical design is the use of street grids which help to relieve congestion resulting from more compact development.  A concern is potential higher costs from increased street mileage.  However, much of this can be offset by reductions in street widths in accordance with the Congress for New Urbanism Designing Walkable Urban Thoroughfares: A Context Sensitive Approach.  Traditional Neighborhood Development (TND) complements street grids in residential areas.  Single family homes in TNDs tend to be multi-story to reduce footprints on lots with widths of about 25’ to a maximum of about 60.’

 

TND typically has home frontages set back about 30’ or less from the nearest street curb.  Conventional residential street widths tend to be at least 30’ from curb to curb to allow for two vehicles to pass easily with parking on one side.  These street widths are often up to 35’ to 40’ or more to allow for parking on both sides.  Such over-sized design is usually driven by the concern to ensure quick and unimpeded access by emergency vehicles.  The reality is that, apart from arterials and collectors, these widths are rarely needed.  Ideal and efficient residential street form allows for curb parking while ensuring traffic flow in at least one direction.  This calms traffic and reduces the chances for accidents.  When vehicles moving in opposite directions meet, one needs to wait behind a parked car for the other to pass.  In a worst case scenario, a fire truck responding to an emergency and meeting a car from the opposite direction might require the car to back up and could delay the response briefly.  Intuitively, this is acceptable as the odds of it occurring are not high enough to justify eternal costs related to maintenance of oversized streets and increased travel from related low density development.

 

Visual preference surveys tend to show that people prefer human-scale development that creates a sense of place while encouraging pedestrian activity and interaction between neighbors.  See results like this from such a survey conducted for the Winnebago County, Illinois Land Resource Management Plan in 2006-2007. To create a sense of enclosure both on the street and within the neighborhood, a general rule of thumb is that the distance between home frontages across the street from each other should be no more than about three times the typical building height.  Consequently, frontages of two-story homes about 30’ in height on a 20’ wide street should not be set back from the nearest curb by more than 35.’

 

The diagram below depicts three scenarios for neighborhood design to accommodate 48 houses.  Each of the figures is presented in a rectangular format for ease of comparison.  The diagrams are primarily to demonstrate differences in the amount of land needed and the level of impervious surface.  Figure B represents conventional layouts of residential subdivisions that became more prevalent in the post-World War II period.  Homes in this scenario tend to be single-story with expansive footprints on large lots fronted by three-car garages along wide streets.  As a result, the 48-lot development uses about 28.5 acres of land.  About one-third of this or 9.3 acres is impervious surface.

 

Figure A shows an example of TND with street widths about 25% less than in Figure B and the addition of alleys.  The TND depicts more moderately sized two-story houses with less than one-third the footprint of conventional homes.  Lot sizes and widths are much less than one-half of the conventional design.  Further, Figure A uses only about 10.4 acres of land or almost one-third less than the conventional development.  The proportion of impervious surface goes up slightly with the TND design but the total is reduced from 9.3 acres to 3.9 acres.  Included is a reduction of about one-third in the use of pavement or other surfacing for vehicles.  This is despite the use of alleys which often give the impression of an excessive extravagance requiring more public upkeep.  Essentially, alleys are common driveways that virtually eliminate the needs for private vehicle entrances.

 

Figure C is an alternate TND that is more moderate in the differences with the conventional design.  It eliminates alleys while using a mix of front and rear-loaded garages.  Consequently, the TND advantages in terms of land use and impervious surface are not quite as dramatic as the design with alleys.  However, the design in Figure C may be more tolerable by community stakeholders that often will insist upon the availability of homes with attached garages.