U.S. Department of Transportation
Federal Highway Administration
|Subject:||Information: Revisions to the Controlling Criteria for Design and Documentation for Design Exceptions||Date:||May 5, 2016|
|From:||/s/ Original signed by:
Acting Director, Office of Program Administration
|Reply to Attn. of:||HIPA-20|
|To:||Director of Field Services
Director of Technical Services
Federal Lands Highway Division Engineers
This memorandum supersedes prior guidance regarding the controlling criteria for design, first established in 1985. For projects on the National Highway System (NHS), a design exception is required to justify not meeting any of the controlling criteria. The revisions below are effective immediately. Divisions should work with their State Transportation Agency (STA) to update Standard Operating Procedures, existing guidance and manuals.
On October 7, 2015, FHWA published a notice in the Federal Register soliciting comments on proposed changes to the 1985 policy establishing 13 controlling criteria for design. The October notice clarified when design exceptions are required and the documentation that is expected to support such requests. After considering the comments received, FHWA published a final notice (attached) in the Federal Register on May 5, 2016.
The following 10 criteria are considered controlling for the design of projects on the NHS: Design Speed, Lane Width, Shoulder Width, Horizontal Curve Radius, Superelevation Rate, Stopping Sight Distance, Maximum Grade, Cross Slope, Vertical Clearance, and Design Loading Structural Capacity. Stopping sight distance (SSD) applies to horizontal alignments and vertical alignments except for sag vertical curves. Of the 10 controlling criteria, only design loading structural capacity and design speed apply to all NHS facility types. The remaining eight criteria are applicable only to "high-speed" NHS roadways, defined as Interstate highways, other freeways, and roadways with a design speed greater than or equal to 50 mph (80 km/h).
As codified in 23 CFR 625.3(f), 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 625. 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, are required for projects on the NHS only when the controlling criteria described above 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.
- Comparison of the safety and operational performance of the roadway and other impacts such as right-of-way, community, environmental, cost, and usability by all modes of transportation.
- Proposed mitigation measures.
- Compatibility with adjacent sections of roadway.
The level of analysis should be commensurate with the complexity of the project.
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:
- Length of section with reduced design speed compared to overall length of project
- Measures used in transitions to adjacent sections with higher or lower design or operating speeds.
- Design Loading Structural Capacity exceptions:
- Verification of safe load-carrying capacity (load rating) for all State unrestricted legal loads or routine permit loads, and in the case of bridges and tunnels 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 decisions.
The approval of deviations from applicable design criteria are to be handled as follows:
- NHS roadway and controlling criteria not met: In accordance with 23 CFR 625.3(f), design exceptions are required and FHWA is the approving authority, or exceptions may be approved on behalf of FHWA if an STA has assumed the responsibility through a Stewardship and Oversight agreement, with documentation as stated above.
- NHS roadway and non-controlling criteria not met: STA is the approving authority for design deviations,1 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.
- Non-NHS roadway and State design criteria not met on Federal-aid projects: STA is the approving authority for design deviations in accordance with State laws, regulations, directives, and safety standards. States can determine their own level of documentation depending on State laws and risk management practices.
States may adopt policies that are more restrictive than the revised FHWA policy outlined above. The FHWA encourages agencies to work together with stakeholders to develop context sensitive solutions that enhance communities and provide multiple transportation options to connect people to work, school, and other critical destinations. It is important to note that the Fixing America's Surface Transportation (FAST) Act of 2015 includes new provisions encouraging design flexibility. The FHWA also issued a memorandum in 2013 expressing support for taking a flexible approach to bicycle and pedestrian facility design. The memorandum is available at https://www.fhwa.dot.gov/environment/bicycle_pedestrian/guidance/design_flexibility.cfm.
Should you have any questions, please contact Elizabeth Hilton at 512-536-5970 or Naureen Dar at 614-280-6846.
Attachment: Federal Register Notice published May 5, 2016
1 The term "deviation," when used in this document, refers to any departure from design criteria that does not require FHWA approval because either the criteria is non-controlling or the facility is not on the NHS. States often refer to these instances as design deviations or variances.