2012 ZONING SERIES
MAY 2012
Country Roads, City Streets, Suburban…Stroads?
By: Jim Brueckman, AICP, City of Rochester Hills
The first two installments of this series examined how street design and development on property along the
street together create character of place. Some places have better character than others of course, and this
series is primarily about how to maximize the quality of place through zoning and development tools.
This month’s article will focus primarily on street design. This is not a subject where zoning typically has
much to say, but it is a critical component in the overall quality and sustainability of a community. Despite
our current typical state of affairs, it is a subject over which local planning and zoning can have a say.
It is important to note that this issue owes a strong debt to Charles Marohn and his Strong Towns initiative
(www.strongtowns.org). Mr. Marohn is an engineer and Strong Towns has a strong focus on creating
infrastructure that we can actually maintain over the long run (hint – we cannot maintain what we have
today). “Stroad” is a term coined by Mr. Marohn and is a perfectly descriptive term for the problem with
hybrid road/streets.
Unfortunately, the planning profession sometimes suffers a lack of professional standardization and
specificity. This lack of common terminology makes it difficult to talk to each other with perfect clarity
of intent and meaning (let alone the associated fields of law, economics, and engineering). One
example is the lack of a standardized usage of the terms “road” and “street.” In practice, road is more
commonly used but in fact, many roads actually function as streets.
Roads Provide Mobility, Streets Provide Access
Roads connect two places and their primary purpose is to move people from point A to point B in the
fastest and most efficient manner. Roads should have travel speeds of 50 miles an hour or greater.
High travel speeds of course require design standards that provide for vehicle safety.
Streets are activity centers that provide access for people and vehicles and are designed as truly public
spaces that are hospitable to a wide range of uses including access to land, walking, socializing, and
driving. All of these uses should have equal weight in the design process. Streets should have travel
speeds of 30 miles per hour or less to provide for pedestrian comfort and safety and should allow for
building design that is legible to a person walking at 3 mph, rather than being designed to be legible
to a driver traveling at 45 mph. Figure 1 summarizes a wide body of research on the subject of the
effect of vehicle speed on pedestrian fatalities.
Figure 1. Effect of Speed on Pedestrian Fatalities
Image Source: peds.org
A quick way to conceptualize the difference is to remember that John Denver sang about country
roads, not country streets. On the other hand, towns and cities have main streets, not main roads.
Based on this conceptualization, roads are rural and streets are urban. The problem arises when we try
to combine the function of roads and streets into a dysfunctional hybrid – stroads.
If roads function best when average speeds are 50 mph or greater, and streets function best when
speeds are below 25 mph, then there is a middle area between 25 and 50 miles per hour that is
appropriate for neither a road nor a street. This kind of road/street – or “stroad” - tries to provide the
mobility function of a road and the access function of a street, and does neither function well. The
stroad is the futon of the transportation field – it combines the mobility and access functions and is
typically barely functional at both. And much like futons, I’m not sure who would prefer to drive on a
stroad instead of a true road or true street. Unfortunately the vast majority of suburban, exurban, and
semi-rural places are dominated by stroads.
How Did We End Up With Stroads?
In most suburban communities stroads began life as roads. Honest to goodness country roads that
traveled through farms and fields. Some roads connected towns, and these were later designated as
major arterials with high traffic volumes as they mutated into stroads. Other roads provided access to
the farms and connected to the roads that led to town – these became the minor arterials and
collector streets in the road classification scheme commonly used today.
Arterial roads carried increasingly more traffic as the community developed and there was greater
pressure for commercial development to occur – for shops and offices to serve the growing
population. It is important to remember that the value of a road is the speed and efficiency that it
provides for the movement between places, and anything that reduces that speed and efficiency
reduces the value of the road. Numerous curb cuts and turning movements increase traffic
congestion, require more traffic lights, and induce more traffic – all of which severely hamper the
efficient and rapid movement of traffic along roads.
The result in most communities has been the transformation of roads into bewildering stroads. These
stroads feature through traffic desperately trying to make it through the tangle of traffic lights and
turning movements, while dodging the people trying to get into the shopping center, office complex
or apartment complex. Woe to the brave or unfortunate soul who, in this hostile environment,
suddenly transforms from a human being into a “pedestrian” as they try to walk to their destination
through the sound and the fury of the vehicular maelstrom raging around them.
It seems obvious that we should take care in our plans to avoid creating stroads, and to reform our
zoning ordinances to stop allowing for stroad-style development. A common tactic is using access
management techniques as a response. Access management seeks to remedy the stroad situation by
reducing conflicts to swift traffic movement and by helping roads meet their mobility function by
managing and limiting the access function.
But What About Streets?
Great streets that are designed as true public spaces with low-speed vehicle traffic that are inviting to
people and bicyclists are one of the keys to creating a healthy and desirable community. Streets thrive
when development is closer together, creating synergies between land uses and higher value-peracre yields and subsequent higher tax revenues necessary to support infrastructure maintenance. 1
It takes a conscientious effort to create great streets because nearly every standard and regulation we
have today has trickled down from design standards for high-speed vehicle traffic. In many cases
highway design standards are misapplied to streets that are intended to provide local access in a lowspeed environment. As a result, there is a tendency for design standards to turn streets into stroads.
This is part of the reason why most of our public ways are actively hostile to pedestrians and bicyclists
– even streets that are designed as vibrant multi-modal spaces.
So what does it mean to say that highway standards are misapplied to streets? Basically, the bulk of
our wisdom in vehicle transportation design comes from research and experimentation in designing
highways. These design standards have been tweaked and adjusted over the years. It is imperative to
remember that the design standards were developed for high-speed, limited access freeways and
then were adjusted to be scaled down to streets. The beginning presumption is that high-speed
vehicle traffic is the key goal on all roads and streets, even though high-speed traffic is not appropriate
on local-access streets.
1 By way of example, Rochester has property values of $500,000 to $1.4 million per acre along streets in the community.
Property values in the much larger shopping centers along the stroad portion of Rochester Road are $150,000 to
$300,000 per acre, despite the necessity to maintain much greater road infrastructure.
The practical impacts of this are enormous. High speed highway driving rests on the concept of
providing an environment where drivers can make mistakes without fatal consequences. These kinds
of forgiving roads minimize the complexities of driving by widening lanes, flattening hills,
straightening curves, adding wide shoulders, using turn lanes, and removing items from the edge of
the roadway to create a wide clear zone. The idea is to provide a wide safety margin to prevent
disasters when a car traveling 70mph goes off the road.
These standards are beneficial and necessary for high-speed roads, but disastrous and unnecessary
when applied to streets which have many intersections and access functions. Implementing wide
travel lanes, turn lanes, and wide clear zones on streets gives drivers a false sense of security and
encourages speeding in a complex environment. Further, these standards cause aesthetic
degradation by taking beautiful and pleasant streets and turning them into bland, ubiquitous
concrete-scapes without beauty or lovability.
In order to move past the default transportation design position to apply high-speed design standards
to what should be designed as streets, it is important to clearly identify which public ways should be
roads and which should be streets in the community’s land use and transportation plan. It is also
imperative to have appropriate design standards for each.
Road Design Standards
Road design standards are easy – simply apply the highway design criteria that are standard operating
procedure today. The community should implement access management standards (MDOT has a
good model ordinance that you can use) to minimize intersections in commercial areas, and
implement design standards in the subdivision control ordinance to control intersection spacing in
residential areas. 2 The land use plan should limit commercial uses along roads unless access
management standards are in place. Planning for a street network that is accessible by foot or bike to
neighborhood areas and connects to the road network is an optimal arrangement, but altering
existing land use patterns is a long-term enterprise.
Street Design Standards
Street design is more difficult because it is not currently the default design option. The default design
option is for high-speed vehicle traffic, and this is entirely appropriate on highways and roads. Streets,
however, should be livable friendly places that enhance the quality of public space. Public right-ofway is the largest percentage of public space in most communities and it is the most important factor
in determining the community’s physical character.
A good access management primer is available at:
http://ops.fhwa.dot.gov/access_mgmt/presentations/am_principles_intro/index.htm. The study notes that access
management increased average speeds on some roads from 38 to 48 mph, which is close to the 50 mph target for an
efficient road.
2
Street design should place livability and human comfort as the highest priority. Specifically, the
following elements are characteristic of a healthy street:
•
Proportion. The street has edges that provide context within the street space. Buildings and
trees most often provide this context, and the height to width ratio does not exceed 1 to 4 (i.e.
the height of buildings is equal to or greater than 4 times the distance between building faces
on each side of the street).
•
Buffer from Traffic. Streetscape features such as trees, planters, or on-street parking lanes are
present to buffer sidewalks from vehicle travel lanes. Street trees should always be permitted
between the sidewalk and the street.
•
Sidewalks. Sidewalks are present along the entire length of the street, and are appropriately
sized to accommodate pedestrian traffic (but in no case are less than 5 feet wide).
•
Geometric Design. Geometric design favors pedestrian comfort rather than vehicle speed.
Increasing a curb radius from 15 to 25 feet can increase pedestrian crossing times by up to 5
seconds, and also encourage cars to travel faster around corners. Curb return radiuses should
be as small as possible, typically 15 feet or less, and additional design measures may be
necessary to provide for pedestrian comfort if curb radiuses are 20 feet or greater.
•
Target Speed (instead of Design Speed). Streets are usually designed to accommodate vehicle
speeds greater than the target speed limit.
•
Building Context. Buildings are designed and located to provide a consistent context along
the street, and are appropriate to the design characteristics of the street. For instance, only
where on-street parking is provided should retail uses be located at the street because retail
uses require convenient parking near the front door. On the other hand, buildings with office
uses may be located close to the street when there is no on-street parking.
•
Aesthetic Amenities. A high level of decorative amenities such as ornamental light poles,
benches, paving, planters, etc. are not necessary to create a great street as long as the other
elements noted above are properly designed. However, aesthetic amenities are desirable if
feasible.
Are Streets Safe?
As noted, transportation engineers and designers often oppose street trees, planters, or other
elements in the right of way on the grounds that a wide travel corridor free from obstacles is needed
to protect the lives of errant motorists. However, empirical studies are starting to show that this is not
the case and that livable, complete streets that are properly designed and that slow traffic
appropriately are actually safer. 3 A study in the Journal of the American Planning Association 4
compared crash incidents along two segments of Colonial Drive (State Route 50) in Orlando Florida.
The following table summarizes the design and performance differences between the two segments:
Characteristic
Length (miles)
Average Daily Traffic
Posted Speed Limit
Lanes
Building Location
Shoulder
Street Section
0.9
47,000
40 mph
4 x 11 ft.
At the street
6.5 ft. parking lane
Avg. Crashes per Intersection
Total Mid-Block Crashes
Injurous Mid-Block Crashes
Fatal Mid-Block Crashes
28
73
42
0
Stoad Section
0.9
46,000
45 mpg
4 x 12.5 ft.
Set back from street
5 ft. paved shoulder + 15
ft. clear zone
27
82
61
6
Difference
------+3.7%
-11%
-31%
-100%
Despite the fact that the two sections carry nearly identical volumes of traffic, the street section with
narrower lanes, buildings at the street, and on-street parking had lower mid-block crash incidents and
dramatically fewer injurious and fatal crash incidents when compared to the stroad section which had
wide travel lanes and larger building setbacks.
This point is worth repeating - not only are properly-designed streets safer for pedestrians, the
empirical evidence suggests that they are safer for motorists as well. Trees, planters, an on-street
parking lane and/or other appropriate elements between travel lanes and the sidewalk provide a
buffer between the sidewalk and the moving cars, which provides a greater comfort for pedestrians
on the sidewalk and creates lower travel speeds which dramatically increase driver safety.
This evidence is supported by research from the field of psychology which has focused on how
individuals adapt their behavior to perceived risks and hazards. Basically, the theory of risk-avoidance
states that drivers will weigh the benefits of driving fast against how dangerous they perceive such
behavior to be. Where hazards are present and visible, such as in the case of livable streets, drivers
perceive high-speed travel to be too risky and so they slow down and pay better attention. On the
other hand, stroads that are designed to eliminate potential roadside hazards while still providing
3
The Journal of the American Planning Association has published numerous articles examining street design and safety.
See Travel and the Built Environment by Reid Ewing and Robvert Cervero in Volume 76, issue 3, 2010; and also two other
articles by Eric Dumbaugh (Safe Urban Form and Designing for the Safety of Pedestrians, Cyclists, Motorists in Urban
Environments) attached in .pdf form.
4 Safe Streets, Livable Streets by Eric Dumbaugh, attached in .pdf form to this article.
land access create a false sense of security to drivers and encourage them to drive faster and to
engage in behaviors that increase their risk of being in an accident.
In conclusion, we must renew our focus on creating great streets (and functional roads) in our
communities. As noted throughout this article, creating great streets requires a focus on pedestrianfriendly and traffic-calming design both within and outside of the right-of-way, 5 while functional roads
require the elimination of impediments to efficient high-speed travel.
The following actions will create a functional road and street network that avoids the stroad pitfall:
•
Establish a clear distinction between roads and streets in the land use and transportation
plans. Emphasize efficient high-speed travel along roads and low-speed land access along
streets.
•
Implement access management standards along roads.
•
Revise zoning standards to allow for walkable development along streets. Include street
design standards in the zoning ordinance for new streets in commercial areas.
•
Adopt new engineering design standards for streets. Highway levels of geometric design that
encourage high-speed travel is the orthodox position today in road design, and road agencies
and transportation engineers will likely object to livable street design elements. This position
is so ingrained in the profession that a few research studies from JAPA likely will not carry the
day, so it will likely take conscious efforts to convince risk-averse transportation engineers and
designers to use the flexibility granted to them by the Green Book. It may be useful to point
out that traffic calming measures used by transportation engineers operate to reduce crashes
by introducing elements that make drivers less comfortable traveling at high speed. Moving
the needle on street geometric design with road agencies and transportation engineers will
require advocacy, negotiation, or whatever other methods of persuasion you can muster.
The Institute of Transportation Engineers’ recommended practice Designing Walkable Urban Thoroughfares: A Context
Sensitive Approach is the basis for the road design recommendations presented herein. It was developed by
transportation engineers and represents a significant step forward in designing great streets. Despite the “urban” in the
title, it contains recommendations that are appropriate for streets in any type of community. You can download it for free
at: http://www.ite.org/css/
5
The following articles and resources can provide a basis of fact to support your arguments in
favor of safer roads and streets instead of inefficient and unsafe stroads.
•
Eric Dumbaugh & Robert Rae (2009): Safe Urban Form: Revisiting the Relationship Between
Community Design and Traffic Safety, Journal of the American Planning Association, 75:3, 309329
To link to this article: CLICK HERE or follow http://dx.doi.org/10.1080/01944360902950349
•
Eric Dumbaugh & Wenhao Li (2010): Designing for the Safety of Pedestrians, Cyclists, and
Motorists in Urban Environments, Journal of the American Planning Association, 77:1, 69-88
To link to this article CLICK HERE or follow http://dx.doi.org/10.1080/01944363.2011.536101
•
Eric Dumbaugh (2005): Safe Streets, Livable Streets, Journal of the American Planning
Association, 71:3.
To link to this article CLICK HERE or follow
http://www.planningmi.org/downloads/dumbaugh_safe_streets_livable_streets.pdf
Series author Jim Breuckman , AICP, is the Manager of Planning for the City of Rochester Hills. Jim has been
a professional planner for over 10 years as a consultant with McKenna Associates, and in the public sector
with Rochester Hills. His experience includes preparing and updating master plans and zoning ordinances
for dozens of communities in Michigan, Ohio, and Indiana with an emphasis on practical and realistic
design-based planning and zoning. He has also conducted numerous economic feasibility studies and
market studies for residential, retail, office and industrial uses.