Five steps to sustainable “complete streets” for Houston
Five steps to sustainable “complete streets” for Houston
A “complete street” accommodates all users: motorists, pedestrians, bicyclists, and
transit riders. Historically, City policy has focused only on motorists. As Houston
grows denser, existing neighborhoods redevelop, transit service improves, and
demand increases for more sustainable places to live, the needs of other street users
become increasingly important.
The biggest impediment to complete streets in the City of Houston is the city itself.
All street construction in the city is governed by the Department of Public Works
and Engineering’s Infrastructure Design Manual, the most recent version of which
was released in 2009. This document is the DNA of our streets; its rules and
recommendations are literally cast in concrete all over our city. If we want better
streets, we need a better Design Manual.
The Design Manual is based on national standards. Its basic approach reflects the
approach of the standards it was developed from, particularly AASHTO’s “A Policy
on the Geometric Design of Highways and Streets,” the so-called “Green Book” which
is on the shelf of every traffic engineer in the country. However, these national
standards have changed. The Green Book now reflects pedestrian needs, and new
standards like the Institute of Transportation Engineers “Designing Walkable Urban
Thoroughfares” are designed to create pedestrian- bicycle- and transit-friendly
streets without compromising the safety or mobility of motorists. Other cities have
adopted more flexible standards.
D R A F T
This document proposes five changes to the Design Manual that will make streets
better for everyone.
New York City Department of Transportation: Design Manual, 2009:
Engineering, planning and urban design best practices over the last ten years
have emphasized a more balanced idea of street design, giving equal weight to
transportation, community, and environmental goals. Practitioners (and the
public) have learned that investment in high–quality street infrastructure can
yield benefits well beyond simple mobility: public health, improved physical
environment, and (particularly relevant in lean fiscal times) economic benefits
in the potential for increased residential and commercial property values and
retail activity.
Christof Spieler, spieler@alumni.rice.edu, November 12, 2010
Five steps to sustainable “complete streets” for Houston
1. Create standards for conditions with constrained right of way
Why this matters:
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Most of the development in the City of Houston is occurring on existing
streets, not in new greenfield plots.
Whenever an existing street undergoes a major reconstruction, it is
redesigned to current standards.
Widening the right of way of an existing street is expensive and is likely to
displace homes, business, and historic buildings.
In a limited right of way, it becomes necessary to balance different portions
of the street. Engineers need guidance for that.
Current city standards:
Street sections shown in the manual are standards for new greenfield streets with
rights of way of 80 to 140 feet for thoroughfares and 50 to 70 feet for local streets.
Most existing streets in the city have narrower rights of way. No guidance is
provided for narrower rights of way.
Recommended new standards:
Create a minimum and desired width for all street elements and a set of guidelines
for which element to favor when right of way is limited.
D R A F T
Precedents for new standards:
New York City Department of Transportation: Design Manual, 2009:
“In a city with as many varied and complex conditions as New York, designs
must be tailored for the particular needs and opportunities created by the local
context, uses, and dimensions of streets. Therefore, the Street Design Manual
leaves ample room for choice, and all designs remain subject to case–by–case
NYC DOT approval based on established engineering standards and
professional judgment, with the safety of all street users being of paramount
importance.”
ITE: Designing Walkable Urban Thoroughfares: A Context Sensitive Approach, 2010:
“The objectives of this report are to …
Describe the relationship, compatibility and trade-offs that may be appropriate
when balancing the needs of all users, adjoining land uses,
environment and community interests when making decisions in the project
development process; …
Provide criteria for specific thoroughfare elements, along with guidance on
balancing stake- holder, community and environmental needs and constraints
in planning and designing walk- able urban thoroughfare projects.”
Christof Spieler, spieler@alumni.rice.edu, November 12, 2010
Five steps to sustainable “complete streets” for Houston
2. Minimize lane widths in urban areas
Why this matters:
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In limited right of way, wider lanes mean narrower sidewalks and smaller
street trees.
Wide lanes increase pedestrian crossing distance.
Wide lanes encourage speeding and increase pedestrian mortality.
Current city standard:
12 foot lanes (Infrastructure Design Manual p. 10-19 – 10-22). Exceptions are
sometimes made.
Recommended new standards:
Minimum 10 foot lanes, with minimum 11 foot curb lanes on streets with volumes
of buses or trucks.
Precedents for new standards:
AASHTO: A Policy on the Geometric Design of Highways and Streets, 2001:
Lane widths may vary from 10 feet to 12 feet. Lane widths of 10 feet should be
used in highly restricted areas with little or no truck traffic. Lane widths of 11
feet are used quite extensively for urban arterial street designs. The 12 foot
lane widths are most desirable and should be used, where practical, on higherspeed, free flowing principal arterials. Under interrupted flow operating
conditions at low speeds (45 mph or less) narrow lane width are normally
adequate and have some advantages. (p. 476-477)
D R A F T
ITE: Designing Walkable Urban Thoroughfares: A Context Sensitive Approach, 2010:
“…on the lower-speed urban thoroughfares addressed in this report (tar- get
speeds of 35 mph or less), a range of lane widths from 10 to 12 feet on arterials
and 10 to 11 feet on collectors is appropriate. On arterials with target speeds
below 30 mph, widths in the lower end of the range are appropriate (10 to 11
feet). On collectors with a target speed below 30 mph, a 10-foot lane width may
be appropriate unless the following design considerations or other factors
warrant a wider lane. Turn lanes that are 10- to 11- feet wide are appropriate
in urban areas with target speeds of 35 mph or less.”
“Modern buses can be 10.5 feet wide from mirror to mirror and require a
minimum 11-foot- wide lane on roadways with 30 to 35 mph target speeds.”
NCHRP: Report 330 Effective Utilization of Street Width on Urban Arterials,
Transportation Research Board, Washington, D.C., 1990:
“Narrower lane widths (less than 11 ft) can be used effectively in urban arterial
street improvement projects where the additional space can be used to relieve
traffic congestion or address specific accident patterns.”
“All projects evaluated during the study that consisted exclusively of lane widths of
10 feet or more resulted in accident rates that were either reduced or unchanged.”
Christof Spieler, spieler@alumni.rice.edu, November 12, 2010
Five steps to sustainable “complete streets” for Houston
3. Provide tight curb radii in urban areas
Why this matters:
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Wide curb radii reduce space for pedestrians at intersections, where
pedestrians are most likely to linger.
Wide curb radii increase pedestrian crossing distance.
Wide curb radii encourage speeding and increase pedestrian mortality
D R A F T
Current city standard:
25 to 40 feet (Infrastructure Design Manual p.10-22)
Recommended new standards:
5-15 feet
Precedents for new standards:
AASHTO :A Policy on the Geometric Design of Highways and Streets, 2001:
When pedestrians encounter an intersection, there is a major interruption in
pedestrian flow. The sidewalk should provide sufficient storage area for those
waigting to cross as well as an area for pedestrian cross traffic to pass (p.99)
ITE: Designing Walkable Urban Thoroughfares: A Context Sensitive Approach, 2010:
“Drivers of large vehicles expect to be able to negotiate turns easily. In urban
areas, however, expectations based on rural and suburban experiences are
unreasonable. Intersection users in urban areas will experience delays and
conflicts between vehicles, pedestrians and bicyclists. Driver expectations need
to shift toward taking turns with other modes and a sense of uncertainty, which
creates a slower, vigilant and safer environment.”
“In urban centers (C-5) and urban cores (C-6) at intersections with no vehicle
turns, the minimum curb return radii should be 5 feet.
Christof Spieler, spieler@alumni.rice.edu, November 12, 2010
Five steps to sustainable “complete streets” for Houston
A curb return radius of 5 to 15 feet should be used where:
1. High pedestrian volumes are present or reasonably anticipated;
2. Volumes of turning vehicles are low;
3. The width of the receiving intersection approach can accommodate a
turning passenger vehicle without encroachment into the opposing lane;
4. Large vehicles constitute a very low proportion of the turning vehicles;
5. Bicycle and parking lanes create additional space to accommodate the
“effective” turning radius of vehicles;
6. Low turning speeds are required or desired; and
7. Occasional encroachment of turning school bus, moving van, fire truck, or
over- sized delivery truck into an opposing lane is acceptable.”
New York City Department of Transportation: Design Manual, 2009:
“All roadway corners should be designed with the smallest possible radius that
still accommodates the design vehicle and emergency vehicles.”
The University of North Carolina Highway Safety Research Center: walkinginfo.org:
“One of the common pedestrian crash types involves a pedestrian who is struck
by a right-turning vehicle at an intersection. A wide curb radius typically
results in high-speed turning movements by motorists. Reconstructing the
turning radius to a tighter turn will reduce turning speeds, shorten the crossing
distance for pedestrians, and also improve sight distance between pedestrians
and motorists.
Nearby land uses and types of road users should be considered when designing
an intersection so that curb radii are sized appropriately.
Where there is an on-street parking and/or bicycle lane, curb radii can be even
tighter, because the vehicles will have more room to negotiate the turn. Curb
radii can, in fact, be tighter than any modern guide would allow: older and
some neo-traditional cities frequently have radii of 3 to 4.6 m (10 to 15 ft)
without suffering any detrimental effects.”
D R A F T
Christof Spieler, spieler@alumni.rice.edu, November 12, 2010
Five steps to sustainable “complete streets” for Houston
4. Provide marked pedestrian crossings at all intersections,
signalized or unsignalized, and allow midblock crossings
Why this matters:
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Pedestrians move slowly compared to cars or bikes, so a small detour can be
a major impediment.
Intersections with no crosswalks send a clear signal that pedestrians are not
welcome.
Current city standard:
Infrastructure Design Manual p.10-12:
“Mid-block crosswalks are not permitted without approval by City Engineer.
The specific conditions which warrant a mid-block crosswalk must be provided
to support the request for a design variance.”
The city also does not mark crosswalks at any location that does not have a stop sign
or traffic signal, even though it is legal for pedestrians to cross at these locations.
D R A F T
One outcome of this policy is that pedestrians will be able to cross the new light rail
lines only where traffic signals are being installed. To keep through traffic moving,
these signals are often widely spaced. On the East End Line, for example, there will
be no signals and thus no pedestrian crossing between Milby and Eastwood, a
distance of ½ mile. This could mean a 10 minute walk simply to cross the street.
Other cities provide unsignalized crossings in similar loctaions.
Recommended new standards:
Mark crosswalks at all intersections. Provide midblock crosswalks where blocks
pedestrian activity is heavy and blocks are over 400 feet long. Provide crosswalks at
every intersection on transit streets, even if vehicle movements at that intersection
are restricted.
Precedents for new standards:
AASHTO: A Policy on the Geometric Design of Highways and Streets, 2001:
Christof Spieler, spieler@alumni.rice.edu, November 12, 2010
Five steps to sustainable “complete streets” for Houston
Pedestrians tend to walk in a path representing the shortest distance between
two points. Therefore, crossings in additions to those at corners and at
signalized intersections may need to be provided. (p.96)
The number of pedestrian crossings on heavily travelled arterials should be
kept to a minimum,, but in an near developed areas it is usually appropriate to
provide crosswalks at every intersecting street. (p.489)
ITE: Designing Walkable Urban Thoroughfares: A Context Sensitive Approach, 2010:
“Generally, however, consider providing a marked midblock crossing when
protected intersection crossings are spaced greater than 400 feet or so that
crosswalks are located no greater than 200 to 300 feet apart in high pedestrian
volume locations, and meet the criteria below.
Avoid elimination of any travel modes due to intersection design. (p. 177)
Common engineering practice is to exclude marked crosswalks from
intersections without traffic control approaching the crossing. This is due to a
number of factors including avoiding a false sense of security provided by
crosswalks when traffic is uncontrolled, encouraging pedestrian caution when
legally crossing at intersections without crosswalks, as well as raising liability
and maintenance concerns. Indeed, several research studies have shown that
pedestrian-vehicle crash rates are higher at unsignalized intersections with
marked crosswalks versus those without.”
D R A F T
Christof Spieler, spieler@alumni.rice.edu, November 12, 2010
Five steps to sustainable “complete streets” for Houston
5: Increase sidewalk widths
Why this matters:
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Pedestrian activity is key to successful urban neighborhoods, retail districts,
and employment centers.
Sidewalks need to be wide enough to accommodate all users, including the
handicapped and parents with strollers.
Absent good sidewalks, pedestrians may be forced to walk in the street,
endangering their safety.
A wide sidewalk encourages leisurely strolling in groups, helping support
street front businesses.
D R A F T
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Current city standard:
Infrastructure Design Manual: A minimum 8 foot pedestrian realm including a 5 foot
sidewalk. (drawing 02775-01 and p. 10-19 to 10-23 and p.10-32 to 10-42)
Infrastructure Design Manual:
On transit streets and “A” streets:
(1) Minimum Sidewalk Width – 6 feet (must be located within the public right
of way).
(2) Minimum Vertical Clear Zone, a continuous obstacle free path, for a
minimum width of six feet and a minimum height of seven and one-half feet.
On METRO’s current light rail lines, a 6 foot pedestrian realm (all paved, with a 4
foot clear zone) has been permitted.
Christof Spieler, spieler@alumni.rice.edu, November 12, 2010
Five steps to sustainable “complete streets” for Houston
Recommended new standards:
6 foot paved pedestrian clear zone with no obstructions.
10 foot minimum from curb to property line, with 15 foot desired.
Precedents for new standards:
ITE Designing Walkable Urban Thoroughfares: A Context Sensitive Approach, 2010:
Recommended clear pedestrian throughway zone minimum width in constrained
conditions is 5 feet in residential and 6 feet in commercial areas (see Table 5.2 in
Chapter 5).
For very high pedestrian volume areas, such as subway exits, transit transfer
points and assembly arena entrances and exits, additional width and special
design attention, particularly at crossings, should be provided.
USGBC LEED for Neighborhood Development, 2009:
New sidewalks, whether adjacent to streets or not, must be at least 5 feet wide
on residential blocks or 10 feet wide on non-residential or mixed use blocks.
D R A F T
Christof Spieler, spieler@alumni.rice.edu, November 12, 2010