State DOTs get greater flexibility in roadway design


Two new announcements should allow state DOTs across the USA to have greater flexibility in the design of roadways, by relaxing some criteria and placing more emphasis on multimodal issues.

Having announced its intentions in 2015, the Federal Highway Administration (FHWA) has now finalized a trimmed-down list of design criteria for roads on the National Highway System (NHS), in a change that will simplify many projects and give more design flexibility to state and local governments. Instead of the 13 design criteria it had applied to all NHS roads since 1985, the FHWA said it will now apply just 10 criteria to the design of high-speed roads such as interstate highways and other major routes. For low-speed NHS routes, such as urban roads or rural roads that become main streets through smaller cities, it will require designers to use just two criteria.

In a speech at the American Association of State Highway and Transportation Officials’ (AASHTO) annual meeting in September last year, FHWA Administrator Greg Nadeau told state DOT officials to expect a review of the longstanding design criteria. In October his agency published a Federal Register notice that formally launched the review and opened it for two months of public comments, saying it proposed “to refine the focus on criteria with the greatest impact on road safety and operation”. Now it has ended the process and altered decades of regulatory policy. The agency has also issued guidance to clarify when design exceptions are needed, along with documentation requirements, in a guidance memorandum that transmits the policy to its field offices.

The FHWA had proposed eliminating three elements from its list of controlling design criteria – bridge width, vertical alignment and lateral offset to obstruction – and renaming three others. After reviewing comments, the FHWA said that it will apply 10 controlling criteria to the design of high-speed roads on the NHS for traffic operating at 50mph (80km/h) or faster. Those criteria are: design speed, lane width, shoulder width, horizontal curve radius, super-elevation rate, stopping sight distance, maximum grade, cross slope, vertical clearance and design loading structural capacity. On low-speed, non-freeway NHS roads designed for traffic below 50mph, the FHWA will now require only the criteria of design speed and design loading structural capacity.

Bud Wright, AASHTO’s executive director, said, “The change in FHWA policy is a welcome move toward more flexibility for state and local agencies to design roads that fit into their surroundings, balancing safety and operational goals for all modes of travel.”

A committee of top engineers from AASHTO has now adopted a resolution to direct the development of more flexible highway and street design guidance. The organization’s Standing Committee on Highways approved calls for the next update to AASHTO’s design guidelines to better address multimodal issues. An update to AASHTO’s Green Book is currently under development. Formally known as ‘A Policy on Geometric Design of Highways and Streets’, the Green Book consists of research-based, peer-developed guidance that serves as the basis for the design of roads on the NHS, as well as many state and local roads.

“We have seen consistent growth in walking and biking throughout the country, and we also have seen an increase in crashes and fatalities involving them,” said Kirk Steudle, chairman of the Standing Committee and director of Michigan DOT. “Our state agencies need robustly researched guidance on how to best incorporate all modes of travel when designing safe and efficient roadways that serve all users.”

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About Author


Tom has edited Traffic Technology International (TTi) magazine and its Traffic Technology Today website since May 2014. During his time at the title, he has interviewed some of the top transportation chiefs at public agencies around the world as well as CEOs of leading multinationals and ground-breaking start-ups. Tom's earlier career saw him working on some the UK's leading consumer magazine titles. He has a law degree from the London School of Economics (LSE).