Committee calls for multi-modal flexibility in AASHTO roadway design guidelines

Updated Jun 7, 2016

highway workerThe American Association of State Highway and Transportation Officials’ (AASHTO) Standing Committee on Highways has adopted a resolution calling for the group’s next roadway design guidelines offer flexibility to better blend “all modes of travel”.

State departments of transportation engineers make up the committee and recommended the changes to AASHTO’s “A Policy on Geometric Design of Highways and Streets,” which is referred to as the Green Book.

“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,” says Kirk Steudle, committee chair and director of the Michigan Department of Transportation. “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.”

The Green Book includes “research-based, peer-developed guidance that serves as the basis for the design of roads on the National Highway System, as well as many state and local roads.” AASHTO says it is currently being updated.

“Multi-modal design philosophies have been described using a variety of names, including context sensitive solutions; practical design and complete streets,” said Bud Wright, AASHTO executive director. “Regardless of the name, the ultimate goal is always to design a safe transportation system that supports a greater quality of life and robust economy.”

The Standing Committee on Highways resolution, Direction on Flexibility in Design Stands, is as follows:

WHEREAS, The AASHTO A Policy on Geometric Design of Highways and Streets (commonly referred to as the “Green Book”) serves as the preeminent design guidance for streets and roadways in the United States; and

WHEREAS, The Green Book is a research based, peer developed set of design standards, which serves as the basis of design for all roads on the National Highway System, as well as many state and local roads; and

WHEREAS, The next edition of the Green Book is currently under development; and

WHEREAS, Increases in bicycle and pedestrian volumes have been recorded nationwide in large cities, suburbs, and small towns, along with corresponding increases in collisions and fatalities; and

WHEREAS, Funding and right-of-way constraints are a continual challenge for transportation facility owners; and

WHEREAS, Additional, robustly-researched guidance is needed on how best to incorporate other modes of travel when designing safe and efficient roadways that serve all users; and

WHEREAS, The design philosophy that incorporates a multi-faceted approach to street and highway design has been described using various terms, including flexibility in design, context sensitive solutions, practical design, and complete streets; and

WHEREAS, Other publications provide examples for multi-modal street design, but there does not exist research-based, peer-reviewed design guidance that fully address the technical design-related aspects of these issues; and now, therefore, be it

RESOLVED, AASHTO should provide guidance to state DOTs and other users of the Green Book regarding flexibility in design; and be it further

RESOLVED, This guidance should follow the AASHTO model of being research-based and peer-reviewed; and be it further

RESOLVED, The Subcommittee on Design (SCOD) is tasked with developing this guidance, both in the short term (next Green Book edition) and the longer term; and be it further

RESOLVED, This guidance should assist in educating engineers and designers on the flexibility inherent in the Green Book, as well as new and additional guidance on specific design issues; and be it further

RESOLVED, This guidance should address designing in and for a multi-modal transportation system; and be it further

RESOLVED, SCOD should coordinate with and possibly include other AASHTO publications in a future set of flexible design standards; and finally be it

RESOLVED, SCOD should identify gaps in necessary research and develop a plan to fill those gaps.