Revision of Thirteen Controlling Criteria for Design; Notice and Request for Comment |
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Gregory G. Nadeau
Federal Highway Administration
October 7, 2015
[Federal Register Volume 80, Number 194 (Wednesday, October 7, 2015)]
[Notices]
[Pages 60732-60735]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2015-25526]
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DEPARTMENT OF TRANSPORTATION
Federal Highway Administration
[FHWA Docket No. FHWA-2015-0020]
Revision of Thirteen Controlling Criteria for Design; Notice and
Request for Comment
AGENCY: Federal Highway Administration (FHWA), DOT.
ACTION: Notice; request for comment.
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SUMMARY: The geometric design standards for projects on the National
Highway System (NHS) are incorporated by reference in FHWA regulations.
These design standards are comprehensive in nature, covering a
multitude of design characteristics, while allowing flexibility in
application. Exceptions may be approved on a project basis for designs
that do not conform to the minimum or limiting criteria set forth in
the standards, policies, and standard specifications.
The FHWA is updating its policy regarding controlling criteria for
design. The current policy identifies 13 controlling criteria for
design and requires formal design exceptions when any of the 13
controlling criteria are not met. The FHWA intends to further
streamline the controlling criteria, and the application of these
criteria, based on the results of recent research that evaluated the
safety and operational effects of the 13 controlling criteria. The FHWA
also intends to clarify when design exceptions are required and the
documentation that is expected to support such requests. This notice
solicits comments on the proposed revisions to the 13 controlling
criteria for the design of projects on the NHS that require a design
exception when adopted design criteria are not met, in accordance with
FHWA regulations.
DATES: Comments must be received on or before December 7, 2015. Late
comments will be considered to the extent practicable.
ADDRESSES: Mail or hand deliver comments to the U.S. Department of
Transportation, Dockets Management Facility, Room W12-140, 1200 New
Jersey Avenue SE., Washington, DC 20590, or fax comments to (202) 493-
2251. Alternatively, comments may be submitted to the Federal
eRulemaking portal at http://www.regulations.gov. All comments must
include the docket number that appears in the heading of this document.
All comments received will be available for examination and copying at
the above address from 9 a.m. to 5 p.m., e.t., Monday through Friday,
except Federal holidays. Those desiring notification of receipt of
comments must include a self-addressed, stamped postcard or you may
print the acknowledgment page that appears after submitting comments
electronically. Anyone is able to search the electronic form of all
comments in any one of our dockets by the name of the individual
submitting the comment (or signing the comment, if submitted on behalf
of an association, business, or labor union). Anyone may review DOT's
complete Privacy Act Statement in the Federal Register published on
April 11, 2000 (Volume 65, Number 70, Pages 19477-78).
FOR FURTHER INFORMATION CONTACT: For questions about the program
discussed herein, contact Elizabeth Hilton, Geometric Design Engineer,
FHWA Office of Program Administration, (512) 536-5970 or via email at
elizabeth.hilton@dot.gov. For legal questions, please contact Robert
Black, Office of the Chief Counsel, (202) 366-1359, or via email at
Robert.Black@dot.gov. Office hours are from 8:00 a.m. to 4:30 p.m.,
e.t., Monday through Friday, except Federal holidays.
SUPPLEMENTARY INFORMATION:
Electronic Access and Filing
You may submit or retrieve comments online through the Federal
eRulemaking portal at: http://www.regulations.gov. The Web site is
available 24 hours each day, 365 days each year. Please follow the
instructions. Electronic submission and retrieval help and guidelines
are available under the help section of the Web site. An electronic
copy of this document may also be downloaded from the Office of the
Federal Register's home page at: http://www.archives.gov and the
Government Printing Office's Web page at: http://www.access.gpo.gov/nara.
Purpose of This Notice
The FHWA is requesting comment on proposed revisions to the 13
controlling criteria for the design of projects on the NHS that require
a design exception when not met, in accordance with 23 CFR 625.3(f).
Design exceptions are an administrative tool used to document an
engineer's evaluation of possible solutions to a specific design issue,
including the operational and safety performance of each option,
impacts to the human and natural environment, and other factors, and
demonstrating the reasons a particular solution that does not meet
applicable design standards was selected. Many States have their own
process for reviewing design deviations when State or Federal design
criteria are not met. When used in this Notice, the term `design
exception' refers to documentation prepared for projects on the NHS
when a controlling criterion is not met, and that must be approved by
the FHWA or on behalf of FHWA if a State Transportation Agency (STA)
has assumed this responsibility through a Stewardship and Oversight
agreement. Stewardship and Oversight agreements set forth the agreement
between FHWA and each STA on the roles and responsibilities of FHWA and
the STA with respect to Title 23 project
[[Page 60733]]
approvals and related responsibilities and oversight activities. The
FHWA also intends to clarify when design exceptions are required and
the documentation that is expected to support such requests.
Comments received through this Notice will be considered by FHWA
when revising the controlling criteria for the design of projects on
the NHS, as well as design exception documentation and application.
Background
As codified in 23 CFR 625.3 and 625.4, the geometric design
standards for projects on the NHS are A Policy on Geometric Design of
Highways and Streets (2001) and A Policy on Design Standards Interstate
System (2005), published by the American Association of State Highway
and Transportation Officials (AASHTO). Rulemaking is underway to adopt
the current (2011) edition of A Policy on Geometric Design of Highways
and Streets. These design standards are comprehensive in nature,
covering a multitude of design characteristics, while allowing
flexibility in application. As codified in 23 CFR 625.3(f), and in
accordance with the delegated authority provided by FHWA Order
M1100.1A, exceptions may be approved on a project basis for designs
that do not conform to the minimum or limiting criteria set forth in
the standards, policies, and standard specifications adopted in 23 CFR
part 625.
The FHWA issued a policy memorandum on April 15, 1985, available on
the docket for this notice, and on FHWA's Web site at http://www.fhwa.dot.gov/design/standards/850415.cfm, which identified 13
criteria contained in A Policy on Geometric Design of Highways and
Streets and designated them as controlling criteria. The policy
required formal design exceptions when any of the 13 controlling
criteria were not met.
The FHWA proposes to streamline the 13 controlling criteria to
refine the focus on criteria with the greatest impact on road safety
and operation. This streamlined application of the controlling criteria
is consistent with the industry's move toward a modified design
approach, often referred to as performance based practical design
(PBPD), and will reduce the instances when a design exception must be
prepared when applicable design standards are not met for projects on
the NHS. The controlling design criteria set forth in 1985 are: Design
speed, lane width, shoulder width, bridge width, horizontal alignment,
superelevation, vertical alignment, grade, stopping sight distance,
cross slope, vertical clearance, horizontal clearance, and structural
capacity. The term `horizontal clearance' was initially interpreted as
the `clear zone' described in the AASHTO Roadside Design Guide (http://www.fhwa.dot.gov/design/standards/850415.cfm), but in the early 1990s
was clarified to mean `lateral offset to obstruction' as described in
the AASHTO geometric design policies (http://www.fhwa.dot.gov/design/standards/930525.cfm). Recent research, culminating in publications of
the most recent Highway Capacity Manual (2010, Transportation Research
Board) and the Highway Safety Manual (2010, AASHTO), developed much
greater knowledge of the traffic operational and safety effects of the
controlling criteria than was available when they were established. The
NCHRP Report 783 ``Evaluation of the 13 Controlling Criteria for
Geometric Design'' (2014) specifically examined the safety and
operational effects of the existing controlling criteria.
The PBPD is an approach to decisionmaking that encourages
engineered solutions rather than relying on minimum, maximum, or
limiting values found in design criteria. The PBPD is grounded in an
analytic framework that enables transportation agencies to utilize
existing design flexibility and analytical tools in a way that
maximizes benefits while minimizing costs. The PBPD does not disregard
engineering guidance or standards. Rather, flexibility in design
typically requires more information and a higher level of analysis when
defining and deciding on the most appropriate design value for a
particular location. Consistent with FHWA's efforts regarding PBPD and
to ensure that design exceptions are only required for criteria with
significant safety or operational effects, FHWA intends to streamline
the controlling criteria based on the findings of recent research.
Since 1985, the controlling criteria have been applied to all projects,
regardless of roadway type or context. The NCHRP Report 783 found that
the 13 controlling criteria had minimal influence on the safety or
operations on urban streets. On rural roadways, freeways, and high-
speed urban/suburban roadways, a stronger connection to safety and
operations was found for some of the criteria than for others.
Proposed Revisions to Controlling Criteria
Based on the findings of NCHRP Report 783 and FHWA's own assessment
and experience, FHWA proposes to eliminate the following controlling
criteria:
Bridge Width.
Vertical Alignment.
Lateral Offset to Obstruction.
To improve clarity, FHWA proposes to rename the following existing
controlling criteria:
Horizontal Alignment to be renamed Horizontal Curve
Radius.
Grade to be renamed Maximum Grade.
Structural Capacity to be renamed Design Loading
Structural Capacity.
The resulting controlling criteria for design are proposed as
follows:
Design Speed.
Lane Width.
Shoulder Width.
Horizontal Curve Radius.
Superelevation.
Stopping Sight Distance.
Maximum Grade.
Cross Slope.
Vertical Clearance.
Design Loading Structural Capacity.
The FHWA also proposes a revision to the application of the
controlling criteria. Most controlling criteria would apply only to
high-speed [design speed >=50 mph (80 km/h)] roadways. Only design
loading structural capacity and design speed would continue to be
applied to all NHS facility types. Research indicates that the current
controlling criteria are less influential on the traffic operational
and safety performance of low-speed urban and suburban arterials than
other features such as intersection design and access management
strategies. Therefore, consistent with FHWA's risk-based approach to
stewardship and oversight, FHWA intends to focus application of the
controlling criteria on high-speed NHS roadways [design speed >= 50 mph
(80 km/h)]. On low-speed NHS roadways [design speed <50 mph (80 km/h)],
design exceptions are proposed to only be required by FHWA for
deviations from the design speed or design loading structural capacity
criteria. Exceptions to the controlling criteria must be carefully
evaluated and approved by FHWA or on behalf of FHWA if an STA has
assumed the responsibility through a Stewardship and Oversight
agreement.
While all of the criteria contained in the adopted standards are
important design considerations, they do not all affect the safety and
operations of a roadway to the same degree, and therefore should not
require the same level of administrative control. Based on the findings
of recent research and FHWA's assessment and experience, a brief
discussion on each of the proposed changes to the controlling criteria
is provided below.
[[Page 60734]]
Controlling Criteria FHWA Proposes To Eliminate
1. Bridge width is proposed to be removed from the list of
controlling criteria because research found little relationship between
bridge width and crash frequency on rural, two-lane highways and
surmised the same would be true for other roadway types. Lane and
shoulder width criteria apply to roadways and bridges, so any
deficiency in bridge width will require design exception documentation
if the lane or shoulder width criteria is not met under this proposal.
Design criteria allow lesser shoulder width, and therefore lesser
bridge widths, on long bridges [overall length over 200 feet (60 m)].
If the minimum lane or shoulder widths are not provided on a long
bridge, the deviation would be documented as a lane or shoulder width
design exception under the proposed revisions to controlling criteria.
2. Vertical alignment is proposed to be removed from the list of
controlling criteria. Three of the existing criteria relate to vertical
alignment. Crest vertical curve design is covered under the stopping
sight distance criterion. Grade is explicitly covered as a separate
criterion, leaving only sag vertical curve length to be covered under
the vertical alignment criterion. While research has confirmed the
interrelationship between vehicle headlight illuminations, sag vertical
curves, and sight distance to features in the roadway, no relationship
has extended to the effect of these combined elements on crashes.
Furthermore, except when a horizontal curve or overhead structure is
also present, sag vertical curve length is not critical under daytime
conditions when the driver can see beyond the sag vertical curve, or at
night, when vehicle taillights and headlights make another vehicle on
the road ahead visible in or beyond a sag vertical curve.
3. Lateral offset to obstruction is proposed to be removed from the
list of controlling criteria because on rural roadways, the controlling
criterion for shoulder width ensures that there will be at least 18
inches of lateral offset to roadside objects. Lateral offset is most
relevant to urban and suburban roadways to ensure that mirrors or other
appurtenances of heavy vehicles do not strike roadway objects and so
that passengers in parked cars are able to open their doors. While
these are important considerations, they do not rise to the same level
of effect as other controlling criteria proposed to be retained.
Controlling Criteria FHWA Proposes To Retain for Roadways on the NHS
With a Design Speed Equal to or Greater Than 50 mph (80 km/h), Unless
Otherwise Noted
1. Design speed is proposed to be retained as a controlling
criterion for all facilities on the NHS. Design speed is different from
the other controlling criteria in that it establishes the range of
design values for many of the other geometric elements of the highway.
Because of its effect on a highway's design, the design speed is a
fundamental and very important choice that a designer makes. In
recognition of the wide range of site-specific conditions, constraints,
and contexts that designers face, the design standards allow a great
deal of design flexibility by providing ranges of values for design
speed. For most cases, the ranges provide adequate flexibility for
designers to choose an appropriate design speed without the need for a
design exception. If a limited portion of an alignment must be designed
to a lower speed, it is generally more appropriate to evaluate specific
geometric element(s) and treat those as design exceptions, instead of
evaluating an exception for the design speed of the roadway.
2. Lane width is an important design criterion with respect to
crash frequency and traffic operations on high-speed and rural
highways. The design standards provide the flexibility to choose lane
widths as narrow as 10 feet on some facilities.
3. Shoulder width has substantial effect on crash frequency and on
traffic speeds on rural highways.
4. Horizontal curve radius, previously called horizontal alignment,
has a documented relationship to crash frequency on rural highways of
all types. Curve radius also influences traffic operations on urban/
suburban arterials. Superelevation is the other main aspect of
horizontal alignment and is being retained as independent controlling
criterion.
5. Superelevation has a documented relationship to crash frequency
on rural, two-lane highways and research suggests this would also be
true on rural multilane highways and freeways. Superelevation is
generally not provided on low-speed urban/suburban streets.
6. Stopping Sight Distance (SSD) is proposed to be retained as a
controlling criterion because sufficiently long SSD is needed to enable
a vehicle traveling at or near the design speed to stop before reaching
a stationary object in its path. Research found that SSD less than
specified by the design standards for crest vertical curve design,
combined with a hidden feature such as a curve, intersection, or
driveway, resulted in increased crashes on high speed roadways.
Retention of SSD as a controlling criterion will ensure that deviations
from this criterion are examined on a case-by-case basis, to determine
whether site characteristics and crash history are indicative of
potential areas needing attention. From an operational perspective, SSD
generally does not affect operations on freeways under free-flow
conditions. However, when freeways operate at near-capacity, limited
SSD may further reduce capacity below the levels expected based on
current predictive models. These impacts are typically examined during
project development.
7. Maximum grade is proposed as a controlling criterion but minimum
grade is not. The existing controlling criteria of `grade' includes
both maximum and minimum grade. Maximum grade is proposed to be
retained due to its relationship to crash frequency on rural, two-lane
highways and the effect of steep grades on traffic operations on high-
speed roadways. Minimum grade is proposed to be excluded because while
it does influence roadway drainage, minimum grade alone does not ensure
sufficient drainage and does not rise to the level of the controlling
criteria.
8. Cross slope is proposed to be retained as a controlling
criterion to address drainage issues. While research has not been
conducted to determine whether there is a relationship between the
normal cross slope of roadway pavements and crash frequency, our
experience is that inadequate drainage could contribute to vehicle loss
of control under some circumstances. Due to the relationship between
cross slope and drainage, especially when combined with minimum grades,
cross slope is proposed to be retained as a controlling criterion.
9. Vertical clearance is proposed to be retained as a controlling
criterion. While vertical clearance does not affect operations on the
roadway other than for those vehicles that are taller than the
available vertical clearance allows, vertical clearance crashes can
have severe impacts on operations by damaging overpasses and other
structures, resulting in extended road closures. In addition,
inadequate vertical clearance on Interstate freeways impacts military
defense routes and requires additional coordination with the Surface
Deployment and Distribution Command Transportation Engineering Agency.
[[Page 60735]]
10. Design Loading Structural Capacity is related to the strength
and service limit state designs, not to traffic operations or the
likelihood of traffic crashes. Previously called `structural capacity,'
FHWA proposes to clarify that the applicable criterion covered herein
relates to the design of the structure, not the load rating. Design
loading structural capacity is important in maintaining a consistent
minimum standard for safe load-carrying capacity and deviations from
this criterion should be extremely rare. Design loading structural
capacity is proposed to be retained as a controlling criterion
regardless of the design speed for the project. Exceptions to design
loading structural capacity on the NHS could impact the mobility of
freight, emergency and military vehicles, and the traveling public and
requires additional coordination with the FHWA Office of
Infrastructure.
Design Documentation
As codified in 23 CFR 625.3(f), and in accordance with the
delegated authority provided by FHWA Order M1100.1A, exceptions may be
approved on a project basis for designs that do not conform to the
minimum or limiting criteria set forth in the standards, policies, and
standard specifications adopted in 23 CFR part 625. Under this
proposal, formal design exceptions, subject to approval by FHWA, or on
behalf of FHWA if an STA has assumed the responsibility through a
Stewardship and Oversight agreement, would be required for projects on
the NHS only when the controlling criteria are not met. The FHWA
expects documentation of design exceptions to include all of the
following:
Specific design criteria that will not be met.
Existing roadway characteristics.
Alternatives considered.
Analysis of standard criteria versus proposed design
criteria.
[cir] Supporting quantitative analysis of expected operational and
safety performance.
[cir] Right-of-way impacts.
[cir] Impacts to human and natural environment.
[cir] Impacts to the community.
[cir] Impacts on the needs of all users of the facility.
[cir] Project cost.
Proposed mitigation measures.
Compatibility with adjacent sections of roadway.
Possibility of a future project bringing this section into
compliance with applicable standards.
Design Speed and Design Loading Structural Capacity are fundamental
criteria in the design of a project. Exceptions to these criteria
should be extremely rare and FHWA expects the documentation to provide
the following additional information.
Design Speed exceptions must address:
[cir] Length of section with reduced design speed compared to
overall length of project.
[cir] Measures used in transitions to adjacent sections with higher
or lower design or operating speeds.
Design Loading Structural Capacity exceptions must
address:
[cir] Verification of safe load-carrying capacity (load rating) for
all State unrestricted legal loads or routine permit loads, and in the
case of bridges on the Interstate, all Federal legal loads.
The FHWA encourages agencies to document all design decisions to
demonstrate compliance with accepted engineering principles and the
reasons for the decision. Deviations from criteria contained in the
standards for projects on the NHS, but which are not considered to be
controlling criteria, should be documented by the STA in accordance
with State laws, regulations, directives, and safety standards.
Deviations from criteria contained in standards adopted by a State for
projects not on the NHS should be documented in accordance with State
laws, regulations, directives, and safety standards. States can
determine their own level of documentation depending on their State
laws and risk management practices.
The proposed revisions to the controlling criteria and design
documentation requirements will be published in final form after
considering comments received regarding the proposed changes.
The FHWA requests comments on the revised guidance memorandum,
which is available in the docket (FHWA-2015-0020). The FHWA will
respond to comments received on the guidance in a second Federal
Register notice, to be published after the close of the comment period.
That second notice will include the final guidance memorandum that
reflects any changes implemented as a result of comments received.
Authority: 23 U.S.C. 109 and 315; 23 CFR 1.32 and 625; 49 CFR
1.85.
Issued on: September 30, 2015.
Gregory G. Nadeau,
Administrator, Federal Highway Administration.
[FR Doc. 2015-25526 Filed 10-6-15; 8:45 am]
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