Planning: Right-of-ways and Roadways

NB: I believe this topic has been discussed much better many times elsewhere on the net and in print.  I am writing simply to clarify my own thoughts.  I apologize for the primitive graphics

One of the terms I used in my previous post on planning was 'right-of-way' (ROW), which is the public area used for circulation between various private and public properties.  Right-of-way implicitly means publicly-owned, but there are some cases where privately-owned streets function in a similar way.  Those are usually behind gates that exclude most of the public, and are largely confined to car-oriented low-density suburbs.

Rights-of-way vary greatly in size, from the walkways of a traditional Greek island town such as Mykonos to grand boulevards of a capital city such as Paris.  Walkways can be as narrow as a few feet, barely leaving room for two people to pass, but major boulevards can be hundreds of feet wide between the surrounding properties.  Narrow rights-of-way do not have the space to segregate traffic into different lanes - which would be pointless for a footpath to begin with - but wide ones always have multiple divisions, usually including areas for motor vehicles, and pedestrians.  They can also include other linear elements such as medians, curb lawns, drop-off zones, bicycle lanes, bus lanes, parking lanes, tramways, and service roads.

Decisions about the width and contents of a right-of-way are important factors in determining an area's visual character and walkability.  Naturally, a right-of-way needs to reflect the amount of traffic it is expected to receive, which is in part determined by the density of development along it. And in for the foreseeable future, most rights-of-way will include roadways as their main element.  But those roadways should not necessarily be the dominant or overwhelming element if the street is to have any kind of walkability.  A limited-access divided highway is an example of a right-of-way that has absolutely no provision for anything but motor vehicles, though they are uncommon in terms of number.

In the post the previous post I specified a 60' ROW to surround the block size I discussed.  As with the block, it was chosen as a reasonable starting point for a low-density area.  That width allows for a 28' roadway bordered by relatively generous 10' curb lawns and standard 5' sidewalks on each side.  In suburban situations an additional 1' between the sidewalk and the private lots is often public property, but not used for anything in particular.  The narrow unimproved area is treated as part of residences' yards for maintenance and landscaping purposes.  A 5' sidewalk allows for two people to easily pass without touching, and two people to walk abreast without stepping off the pavement.  A 28' roadway allows for parking on one side and vehicular movement in both directions.  Cyclists share travel lanes with motor vehicles, which are usually unmarked.

Now that is only one of a possible number of configurations, but is typical for low-to-medium density suburbs.  But as with any decision, there are trade-offs.

	Square	Square	Mildly Rectangular	Mildly Rectangular
Gross Length	300	300	600	600
Gross Depth	300	300	300	300
ROW width	60	50	60	50
Net Length	240	250	540	550
Net Depth	240	250	240	250
Taxable area	64.0%	69.4%	72.0%	76.4%
Increase	n/a	8.5%	n/a	6.1%

Reducing the ROW width just by 10' results in a significant increase in taxable area.  The reduced ROW would require taking space from one of its element, however.  The sidewalk is already at the American minimum, leaving the curb lawn and roadway as possible sources.  By eliminating parking, the roadway could be reduced to 22' and the curb lawns would remain sizeable at 8'.  Or the curb lawns could be reduced to 5' and the parking could remain.  The arrangement does not have to be symmetrical, of course, and another option would be to have a wide curb lawn measuring 10' on one side, and parking opposite.  Other configurations of a 50' ROW are possible.

The inclusion and sizing of any element in a right-of-way reflects a combination of factors, including cultural values, citizen demand, the typical sizes of vehicles, climate, and cost, which is always involved.  For instance, large commercial vehicles in the the United States are typically 102" wide, filling most of a 10' lane.  Winter storms in Vermont can leave 12-24" of snow, which when plowed from the streets ends up on the sidewalk if the curb lawn is too narrow.  In Tokyo, most residential streets don't have sidewalks because residents are used to sharing narrow streets between pedestrians and vehicles.  And in large portions of low-income countries, there is no infrastructure development whatsoever, due to indifference, corruption, poverty, or all three.

While, arguably, there is no absolute right and wrong here, the decisions about the design of rights-of-way have major influences on the built and natural environment.  Designers should take into consideration not only local practices and expectations, but also global experiences and long-term considerations when working on a new planning document.