RK&K recently concluded a transportation project over a decade in the making for the Pennsylvania Department of Transportation (PennDOT) that provides significant congestion reduction and safety improvement, new pedestrian and bicycle facilities, and more than 40 revised driveway accesses.
Technical Leader Don Lerch, PE, explains that Pennsylvania State Routes (SR) 209 and 115 intersect at a severe skew in the Village of Brodheadsville, Monroe County at the foothills of the Pocono Mountains. SR 209 is a National Highway System route and SR 115 is a federal aid primary route. Both two-lane routes carry over 15,000 vehicles through the intersection daily. The intersection is amidst a mixture of commercial, residential, and educational land uses with the northwest quadrant dominated by the sprawling Pleasant Valley School District campus, where approximately 2,500 students attend classes.
This all combined into the perfect formula for several severe traffic issues.
“Chronic severe congestion and a high crash rate have plagued this intersection and the corresponding approach roadways since an influx of residents migrated from New York and New Jersey in the late 1980s,” said Don.
Failing levels of service and extremely long queues were routine experiences and crash rates exceeded statewide averages for similar facilities fivefold. Don added that compounding traffic operational difficulties were frequent and open-ended access points (both in driveways and Township roads), lack of turning lanes, and concentrated peak periods associated with school traffic combined with commuter through traffic. Plus, pedestrian access facilities were non-existent, and shoulders were narrow.
To begin addressing these numerous issues, PennDOT selected RK&K in 2013 to design a solution to mitigate these difficult traffic conditions.
First, the project team was tasked with developing six alternatives for comparison and contrast.
They completed the alternatives analysis which examined traffic signal and roundabout options. They then completed the preliminary engineering and final design for roundabouts at two intersections, and traffic signals at one intersection.
The selected alternative included widening of over 7,000 feet of roadway to add additional through lanes. The existing signalized SR 209/SR 115 intersection and the primary SR 209 campus driveway intersection were converted into hybrid roundabouts. The primary SR 115 driveway intersection was signalized, and School District security personnel have been provided the capability of overriding the signal phasing during daily bus entry and discharge periods.
This alternative was selected because it provided the best overall corridor level of service and potential for safety improvement. Don said that roundabouts have empirically demonstrated that they have a 30%-40% reduced crash rate and a 70%-80 % reduced crash severity rate when compared to signalized intersections, while still providing a higher level of service. The majority of these crash reductions can be attributed to reduced speeds and much fewer intersection conflict points.
“Navigating through the design process was both challenging and interesting,” said Don.
Public and Stakeholder Involvement
To address concerns from the School District administration members, RK&K’s project management staff attended several school board meetings to explain the differences between roundabouts and traffic circles and the advantages that roundabouts have in comparison to signalized intersections.
Chestnuthill Township was extremely cooperative and worked with the team to develop and execute agreements for sidewalks, lighting, roundabout circle landscaping, and signal/sign maintenance. They requested decorative light fixtures, which were included, and RK&K worked collaboratively with them on a circle landscaping plan.
Stormwater Management
The increased roadway capacity and addition of sidewalks increased the amount of impervious surface by more than 1 ½ acres and the team was challenged to find effective stormwater management. The project is situated over two separate watersheds and Pennsylvania regulations require them to mitigate stormwater flow independently for each watershed.
Additionally, there wasn’t a regulated watercourse within the project limits to outlet to, and infiltration testing results were erratic. The stormwater management plan consisted of the addition of almost two acres of best management practices such as rain gardens, vegetated swales, infiltration trenches, wet ponds, and bioretention basins. This correspondingly increased right of way and environmental impacts. To control the flow of stormwater, over 13,000 linear feet of pipe and more than 170 inlets or manholes were incorporated into the design.
Traffic Control
Constructing a roadway project in an urban or suburban area with high volumes is not an easy task, particularly when there are considerable changes in profile elevations, said Don. Safely maintaining only slightly impeded traffic flow through the construction zone, always keeping access to each individual property, and minimizing construction impact on commercial establishments were paramount to project success. The RK&K project team developed a traffic control plan that included four primary phases and several subphases. In addition, they prepared a lengthy special provision detailing what restrictions the contractor would have in order for businesses to maintain effective internal circulation through temporary construction easement areas. For example, at certain businesses, the contractor was only allowed to enter the temporary construction easement areas during non-business hours and was required to make the area safely passable during business hours. Since construction was scheduled to span four years, the phasing and material applications were designed to accommodate proper surface drainage and effective winter maintenance such as snow plowing. To provide a consistently smooth riding surface, the last phase includes milling the entire project limits and providing the final wearing surface.
Topography and Vertical Geometry
Several topographical features created challenges to establishing vertical geometry for the new project. Both roundabout intersections are located on slight grades. There were several driveway access control points to tie into, many in proximity to the circles. The existing profile exhibited some substandard vertical curves with insufficient stopping sight distance. RK&K worked through all these issues including designing the circles as tilted planes rather than conical with consistent lane cross slopes. Because of the complexity of defining the vertical geometry around the intersections, RK&K produced nine intersection detail plan sheets with approximately one thousand control point elevations.
Project Highlights
This project included:
- 49 right of way claims including two total acquisitions/relocations
- Seven intersecting Township Roads
- Refined access points with 47 driveway revisions and corresponding highway occupancy permit applications
- One underground utility (Williams Pipeline) which had a 40’ wide buffer where excavation was not permitted
- Six overhead utility companies on either PPL Electric or Frontier poles and 71 poles relocated
- Two permits – National Pollutant Discharge Elimination System (NPDES ) and Department of Environmental Protection General Permit
- Sidewalks throughout the majority of the project with ADA compatibility, except where infeasible
- Improved bus pullover area
- Delineated crosswalks and shared-use paths
- Pedestrian-activated rapid flashing beacons at all roundabout crosswalks
- Decorative roundabout lighting and landscaping
- One retaining wall and six special curb designs
