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Alternative Design Options May Benefit Projects

Kyle Leonard

Our nation’s roadway system contains a functional hierarchy which provides each road with a designation based on its primary purpose. At the top of the hierarchy are freeways and expressways designed to maximize “Point A to Point B” mobility that feature limited access, i.e. access at only high speed interchanges, no intersections or driveways. There are also arterials that are roads that have traffic signals at intersections and access points at larger frequency spacing. These arterials are fed by collectors and local streets, which have the main purpose to connect specific activities (residences, retail stores, industries). Put together, this network enables point to point services, a notable advantage the road transport has over other transport modes.

Roundabouts are one of the options available to a transportation planner that help keep traffic moving smoothly.

Roundabouts are one of the options available to a transportation planner that help keep traffic moving smoothly.

Historically in transportation design, form followed function. This relatively simple concept however has become much more complicated as the “function” of roads has grown from getting a car from one destination to another to accommodating mass transit and bicycles, to balancing environmental concerns, stormwater management, and economic development.

Alternative Design

It is now the transportation engineer’s job to recognize locations where alternative designs or multi-modal features may be effective, safe and warranted or where a more direct or single purpose design option is needed. There are situations where mixing vehicles traveling 30 to 55 miles per hour with pedestrians, bicycles and multiple access points is not a good solution. Choosing the correct multi-modal solution is accomplished by listening to residents, businesses and other interested parties to accommodate a diverse set of desires as well as understanding the project must be a functional transportation facility.

Alternative intersection designs look for non-traditional ways to efficiently move traffic and reduce overall delays to the motoring public. Roundabouts, diverging diamond interchanges and continuous flow intersections are all options for designers looking to keep traffic moving smoothly. Many times, the space available and the potential benefits are weighted against how the change is perceived by public. It is important to look for the best solution given the specific project needs and constraints.

Stormwater Management

The roadway project incorporated an innovative stormwater management solution that reused stormwater runoff for golf course irrigation.

The roadway project incorporated an innovative stormwater management solution that reused stormwater runoff for golf course irrigation.

Stormwater management has complicated the project design even further. In the past, the priority was removing water from the roadway. Inlets, pipes, and roadside ditches were all designed to efficiently transport water away from the pavement. Each project is unique and presents differing issues and challenges which are to be resolved through the design process.

An example of how all these competing interests can come together to influence a design, and how designers successfully navigated the challenge can be found in Washington County, Minnesota.

safety & efficiency

The County needed to expand Woodbury Drive from two- to four-lanes over a two-mile segment from Valley Creek Road to Bailey Road. HR Green, as the engineering consultant to Washington County, was tasked with designing this expansion in a way that responded to community interests for safety, mobility, and aesthetics as well as the inclusion of pedestrian and bicycle facilities, but also stayed within a 120-foot right-of-way in some locations. In addition, challenging stormwater management and downstream water quality objectives were identified that required a creative solution to obtain regulatory permits. The existing trail was disconnected, with segments not built and only on one side of Woodbury Drive, which led to safety concerns for bicyclists and pedestrians in the corridor.

Woodbury Drive expanded from a two-lane to four-lane roadway with an adjacent recreational trail.

Woodbury Drive expanded from a two-lane to four-lane roadway with an adjacent recreational trail.

Working with Washington County and the City of Woodbury, MN, HR Green’s design responded to these needs with a new four-lane corridor including two new multi-lane roundabouts, a multi-use trail on both sides of Woodbury Drive which kept bicycles and pedestrians off the road and away from vehicles, aesthetic treatments, and an innovative stormwater reuse solution that responded to concerns about groundwater use for golf course irrigation while also meeting stringent water quality targets from the watershed district.

A resilient and efficient design was created by listening to input from all effected parties, addressing regulatory requirements, considering and using creative design elements and incorporating solutions for pedestrian and bicycle usage in a safe and aesthetically pleasing manner. Pedestrians and bicycles now had a dedicated, complete path separate from the roadway creating a much safer environment. Traffic flow increased by using a roundabout and stormwater management was, not only efficiently handled, but created to benefit a local golf course in an environmentally positive manner.

As the Washington County example illustrates, designers must receive vital public input then examine design options and standards. The goal is to identify alternatives that extend the life of improvements, reduce the cost of maintaining new improvements, and minimize the adverse impacts to the community. An efficiently operating infrastructure is an essential component to a healthy community and prosperous economy.

HR Green’s Engineers are dedicated to finding the right design solution to its client’s challenging road projects. To learn more contact David Dougherty at ddougherty@hrgreen.com

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