Companion Guide to Video August 2012

www.fhwa.dot.gov/federal-aidessentials

Each day, Americans depend on the more than 

4 million miles of Federal, State and local road 

systems that make up our Nation’s highway 

network. We drive these roads to get to work, 

move goods and freight, and to appreciate the 

vastness and wide array of parks, forests, cities, 

museums, beaches and cultures the United 

States has to offer. 

The National Highway System, or NHS, makes

up just a fraction of the Nation’s total road miles, 

yet it carries a significant percentage of all 

traffic. The NHS is a road system classification 

consisting of the Interstate system and other 

roadways of particular importance to the 

Nation’s economy, defense and mobility. The 

State and local road systems make up the vast 

majority of remaining public streets and 

highways, which are also vital to our Nation. 

Agencies at all levels of government are 

responsible for providing motorists a nearly 

uniform level of consistency by building and 

maintaining our Nation’s roads to a common set 

of geometric design features. 

These design features establish 

the physical aspects of our 

roadways like the sharpness of a 

curve or width of a lane.

You, as a local public agency, or LPA, are 

responsible for developing your Federal-aid 

project consistent with the applicable geometric 

design features for the type of highway system 

and type of project. Applying the appropriate 

geometric design features help to ensure the 

safe accommodation of traffic and freight while 

serving our Nation’s strategic and economic 

priorities. 

Geometric design requirements for roadways 

making up the NHS have been established by 

the Federal Highway Administration, or FHWA,

to preserve a high level of mobility and safety. It 

is important for you to understand that the 

design requirements for projects affecting the 

NHS apply regardless of funding source. 

Project Development

Design

Project Geometric Design Requirements

Our Nation’s roads are constructed to specific geometric design 

requirements
Federal-aid Essentials for Local Public Agencies

Federal-aid projects on State or 

local roads must adhere to the 

geometric design requiremements 

established by your State.

The four primary geometric design requirements 

that may apply to your highway project are: 

• AASHTO’s A Policy on Geometric Design of 

Highways and Streets, commonly referred to 

as the “Green Book.” The Green Book is 

maintained by an organization of State 

government transportation officials known as 

the American Association of State Highway 

and Transportation Officials, or AASHTO.

• AASHTO’s A Policy on Design StandardsInterstate System

• Your State’s approved 3R geometric design 

standards

• Other State approved design standards

To determine which design requirements apply 

to your highway project, you first should 

consider the type of project and where it’s 

located. Project types generally fall into one of 

three categories, based on the scope of work: 

(1) new construction or reconstruction projects, 

(2) resurfacing, restoration or rehabilitation 

projects, more commonly referred to as 3R 

projects, and (3) preventive maintenance 

projects. Geometric Design requirements apply 

to projects on one of the following four 

categories of roads: 

• Interstate, 

• NHS freeway, 

• Non-freeway NHS route

• Non-NHS road. 

All new construction and reconstruction projects 

on the NHS, as well as any 3R projects on an 

NHS freeway, must be designed to meet the 

FHWA approved edition of the AASHTO Green 

Book. The FHWA has also approved the use of 

State design manuals in lieu of the AASHTO 

Green Book in some states. Since the 2001 

publication of the Green Book, which serves as 

the current requirement, a 2004 and 2011 

edition have been published, and FHWA, may 

soon adopt the latest version as the new 

requirement.

AASHTO’s A Policy on Design Standards –

Interstate System contains the design 

requirements for all new construction, 

reconstruction or 3R-type projects on the 

Interstate system. 

A 3R-type project located on the NHS but not on 

the Interstate or an NHS freeway may be 

required to be designed according to your 

State’s approved 3R design requirements. If 

your State does not have approved 3R design 

requirements, then either the AASHTO Green

Book or your State’s approved design manual 

requirements apply to your project.

Any preventive maintenance-type project 

located on the NHS must comply with your 

State’s design requirements established for 

preventive maintenance-type projects. You are 

responsible for determining your State’s 

preventive maintenance design requirements as 

they vary in each State. 
Federal-aid Essentials for Local Public Agencies

If you are responsible for any type of project 

located off the NHS that uses Federal-aid funds, 

you must adhere to applicable laws and design 

requirements required by your State. 

The design criteria found in the AASHTO Green 

Book provides substantial flexibility to address 

specific conditions encountered on projects. 

Among the thousands of design features listed 

in the AASHTO Green Book, FHWA recognizes 

the following 13 criteria having considerable 

importance to the operational and safety 

performance of any highway: 

• Design Speed

• Lane Width

• Shoulder Width

• Bridge Width

• Horizontal Alignment

• Vertical Alignment

• Grades

• Stopping Sight Distance

• Cross Slope

• Super-elevation

• Lateral Offset to Obstruction

• Vertical Clearance

• Structural Capacity

The FHWA calls these critical elements the 

“thirteen controlling criteria,” and these cannot 

be deviated from without first coordinating 

approval through your State DOT. 

If you determine that conditions 

warrant an exception to the 

applicable design requirement, 

then follow your State’s 

procedures for requesting a 

design exception.

Design exception requests must consider all 

project conditions, including compatibility with 

adjacent sections of road, and the expected 

length of time before reconstruction of the 

section. Your written request should detail the 

considerations and engineering judgment used 

to analyze and justify the design exception. 

Include details of how you considered the costs 

and impacts of meeting the design criteria, the 

risks involved of not meeting the criteria, and 

any other relevant factors, such as traffic 

volumes or speeds or the extent to which the 

design criteria cannot be met.

If you are considering a design exception, it is 

important to emphasize the mitigation strategies 

you have considered to offset the risks of not 

meeting the design criteria. For example, what 

mitigation strategies could you consider to 

address a sharp, substandard curve ahead? In 

this situation, your goal is to consider features 

proven to help vehicles stay on the road to 

mitigate the risk of building a substandard curve. 

In this example, you could address this situation 

by including mitigation techniques such as the 

installation of warning signs or speed plaques, 

widening the roadway or shoulders, installing 

rumble stripes, adding super-elevation or 

incorporating a skid resistant high-friction 

pavement surface. 
Federal-aid Essentials for Local Public Agencies

Your completed design exception request 

should be forwarded to your State department of 

transportation, or State DOT, which is 

responsible for facilitating the review and 

approval process for design exceptions. Check 

your State DOT’s procedures for design 

exceptions for projects located off the NHS. 

When a design exception is necessary, the key 

issue is to allow adequate time in your project 

planning to get the design exception approved 

so that your construction is not delayed.

Finally, remember that you are required to meet 

these geometric design requirements on all 

Federal-aid projects. Doing so will help you 

avoid any unnecessary delay in receiving 

construction authorization for your Federal-aid 

project.
Federal-aid Essentials for Local Public Agencies

The content of this 

document is not a 

substitute for 

information obtained 

from State departments 

of transportation, 

appropriate FHWA 

Division Offices, and 

applicable laws. 

Scenarios have been 

simplified for emphasis 

and do not necessarily 

reflect the actual range of 

requirements applicable 

to the scenario or this 

topic. This document

was created under 

contract number

DTFH63-12-F-00025 by 

the Federal Highway 

Administration, U.S. 

Department of 

Transportation, and is 

offered to the public to 

heighten and focus 

awareness of Federal-aid 

requirements within the 

local public agencies 

community and 

reinforces the 

importance of these 

necessary policies, 

procedures, and 

practices.

This companion resource 

is the script content for 

the video production of 

the same name. 

Additional Resources

• Information on highway design topics

http://www.fhwa.dot.gov/design/

• Federal regulations on design standards for highways

http://www.ecfr.gov/cgi/t/text/textidx?c=ecfr&sid=34ef730f21ebfc5a205093db12962891&rgn=div5&view=text

&node=23:1.0.1.7.18&idno=23

• Information on how to mitigate challenging design situations

http://safety.fhwa.dot.gov/geometric/pubs/mitigationstrategies/fhwa_sa_070

11.pdf

• Information on designing safe, efficient roads that incorporate community 

values

http://www.fhwa.dot.gov/environment/publications/flexibility/

• Information on the applicability of design standards

http://www.fhwa.dot.gov/programadmin/standards.cfm