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A week ago, someone pointed out that so many of America’s roads were barely walkable because they lacked even sidewalks.  I both agree with this and disagree with it.  Sometimes a sidewalk is more than you need.

A street without sidewalk, skinny enough to enforce caution on drivers, can be perfectly safe to walk in.  Skinnying the street is often helped by allowing on street parking on both sides of the streets.  A car traveling at 10 MPH is not a real danger to a walker or biker who is aware of it.  Two cars traveling at each other at these speeds are even less of a risk, as they must stoop and socially negotiate to figure out how to pass each other.

The sidewalk is only necessary where traffic is too fast for walkers to be in the street in the first place.  The sidewalk is a separate way for walkers, behind the curb.  The curb and sidewalk behind it developed long ago to avoid different hazards.  As long as cities have used horses for industry and delivery, there have been city streets full of horse droppings (and even dropped horses).  Then sidewalk protected walkers from the open sewer of the streets.  To cross the street, walkers would either use stepping stones, look for w a light patch in the streets, or bore sweepers to clear a path through the manure for them.  Much of 17th and 18 century fashion could be traced to the need to keep expensive fabrics out of crap’s way.

With the advent and spread of vehicular traffic that could move over ten times as fast as a horse, sidewalks changed purpose, protecting from injury or death instead of disease.   Where walkers in the busiest cities of 1850 were protected from the leavings of horse traffic, walkers of 1950 were much more concerned by getting killed by the traffic itself.  They were much more safe up on the sidewalk.  Fortunately for walkers, cities were already fitted with sidewalks for the old purpose. Streets without sidewalks had an urgent reason to get some, soon.

The curb that defines the sidewalk is two things, drainage and contract.  A curb defines “closed drainage” where  water that falls on the road flows to the curb and thence to inlet slots in the curb at the bottom of every hill.  Usually, these drainage structures jettison directly into the stream below.  Whatever survives that gout of water can stay, every other species had best have populations miles away in the countryside.  Most aquatic species under these conditions of scour do not survive the year.  This is why freshwater mollusk species are some of the most endangered of any of the world’s phyla.  

A curb is also contract between walker and traffic.  Everything to the right of the curb is safe for walkers, everything to the left of the curb is trafficway.  A walker on the wrong side of the curb can be killed at will, or at least with the change of a radio station or a moment’s admiration of a fast food sign.  All the driver in traffic is liable for is a misdemeanor, unless witnesses can prove that they intuitionally swerved to hit the walker.  Most witnesses at these sorts of things frankly weren’t paying attention, and I trust that most walkers killed in traffic are not killed with malice.  It doesn’t take much will or effort to kill with a 2 ton object traveling at 45 MPH.  Nothing personal.

The emerging policy of complete streets seeks to remedy this by giving every mode of transportation a place to be on  the street and within the right of way.  Clearly delimited bike lanes and transit ways supplement the traffic ways. Sidewalks are mandatory and wide enough for two wheelchairs, or even outdoor seating.  Street furniture and a planting strip with ample open ground for trees both protects walkers and makes the street more enclosed.  A complete street is a wider affair than a simple highway, after all, and walkers might reasonably ask why they feel safe skittering along the edge of this scrim of pavement and lanes without a line of trees, bike racks, restaurant seating, and benches to delineate their realm from that of wheeled vehicles.  

Well-designed complete streets can heal the fundamental rift in American transportation: that all transportation is traffic, and woe betides anyone trying to get anywhere by any other means.

But a complete street is best for a traffic arterial.  There are about a million miles of these in the US, many of them remote country or mountain roads, with no development potential save a few farmsteads and getting traffic from there to wherever.  I haven’t done the GIS clip yet, but I’d expect much less than a quarter of the arterials in the US are urban enough for complete streets.  And there’s 3.5 million miles of other roads to consider. A local road with light enough traffic, should not need more than a lane and a half (18 feet) of through width, and the full design expectation that adults will be walking in the street and children will be playing there.  Some of the nicest streets I’ve seen have no sidewalks, and very slow traffic.  Th curbs have to drain much less rainwater when the street is just narrow enough.

A street can be many things, sometimes it doesn’t even have to be complete to support a diversity of uses.

Friday, I’m going to write a bit about climate change.  I still intend to continue the threads from January and February, but research calls.