Increasing flexibility in multi-modal asphalt road design
By Mat Herron
We demand roads. The nation’s veins and arteries permit commerce to flow freely, allow us to reach that much-needed vacation spot, or simply make it to work on time.
Our drive to drive saturates every aspect of our lives, from the occasional to the habitual: Americans take 1.1 billion trips a day, and travel averages 11 billion miles a day – roughly 40 miles per person, per day, according to the Bureau of Transportation Statistics.
As of 2015, however, a more three-dimensional picture of what we demand from transportation avenues is starting to emerge. One highlight from the bureau’s Transportation Statistics Annual Report reveals that more than 10 percent of commuters in Boston, Pittsburgh, Washington, D.C. and New York City walk to work. Commuters like their bikes in Portland, Oregon, (more than 6 percent) Madison, Wisconsin (5 percent) and Minneapolis (4 percent).
Trends like this are supporting a continued re-evaluation of asphalt road design by both the federal government and state transportation engineers, as they adopt a philosophy of infrastructure that better reflects the growing number of cyclists and pedestrians, not just drivers.
Bradley Wieferich, director of the Bureau of Development for Michigan’s Department of Transportation, said that several of the state’s multi-modal asphalt design projects have been successful. Among them:
• Buffered bicycle lanes were installed with asphalt road resurfacing of M-143 in East Lansing, M-10 in Oakland County and on Nine Mile Road in the city of Ferndale. The M-143 project also included transit pull-offs. The Nine Mile project included green pavement markings “at specific potential conflict points between turning vehicles and bicyclists,” Wieferich said.
• As part of its asphalt resurfacing project for M-43 in East Lansing an asphalt-resurfacing project included the installation of median pedestrian refuge islands.
• In the city of Lansing, a lane reduction on Moores River Drive between Waverly Road and Mount Hope included a pedestrian refuge island, an asphalt sidepath and enhanced pavement markings for crosswalks.
• Also in Lansing on South Washington Avenue, the city performed a full asphalt roadway reconstruction. The reconstruction allowed for a lane reduction from 4-3, landscaped medians, pedestrian refuge islands and bicycle lanes.
To implement multi-modal roadway design statewide, MDOT uses a Context Sensitive Solutions (CSS) process that relies heavily on stakeholder buy-in while taking into account land-use and cultural implications, according to Wieferich.
“For example, in a more rural setting with a lower ADT (average daily traffic), adding a wider paved shoulder to the trunkline may be the best solution for addressing pedestrian, bicycle and transit stop modal needs,” he said. “In a more urbanized setting, where traffic patterns and adjacent land use may be more intensive, separated facilities with buffers may be necessary to provide a safer multi-modal user experience. Using our CSS process, we work through these issues with our stakeholders to best address the needs while utilizing sound engineering judgment in application of design standards and best practices.”
The most important step is involving the community early in the process.
“In order to fully understand and address multi-modal needs of the communities, there must be discussion on existing non-motorized plans or ‘Complete Streets’ policies,” Wieferich said. “We must also understand local destinations and linkages needed for various modes. This engagement helps better understand the environmental and cultural context of the transportation project. This understanding is critical to developing the right solution to multi-modal needs as we move into design.”
MDOT has found that there is no “one-size-fits-all solution” to making an asphalt roadway safe for all modes of transportation, according to Wieferich. The department has been using AASHTO geometric criteria, but it is also beginning to branch out to other resources, such as the urban street and bicycle design guides published by the National Association of City Transportation Officials, to help provide solutions to unique circumstances.
Last fall, the Federal Highway Administration received more than 2,300 comments when it proposed reducing the number of criteria for geometric design, which had been in place since 1985.
“Through the changes in controlling criteria, FHWA gave engineers the flexibility they need to design solutions that address the project goals in a way that is more compatible with communities, while enhancing the safety and operations of roadways on the National Highway System,” said Nancy Singer, a spokesperson for Federal Highway Administration.
States and FHWA division offices are determining what changes to policies and procedures to make in light of the criteria changes, according to Singer.
These changes will facilitate design that better encompasses multi-modal transportation, Singer said, by helping “communities build connected pedestrian and bicycle networks, apply design flexibility and enhance safety for all roadway users while eliminating the time required for FHWA approval of design exceptions on many projects.”