2017 Concept for a Clover Hill Road/Prince William Parkway “Bowtie” Intersection
Recently, the Prince William County Department of Transportation asked for our feedback on their proposed preliminary design for rebuilding the intersection of the Prince William Parkway (Route 234) and Clover Hill Road near Manassas as an “innovative” bowtie intersection, where all direct left turns are eliminated and instead accommodated via two roundabouts on the minor cross street. Our reply is posted below. We will track this upcoming project in the coming years as the design is refined for construction.
Thank you for soliciting Active Prince William’s input on how the redesigned intersection of Clover Hill Road at the Prince William Parkway can best serve people walking and bicycling.
Conventional On-Road Bike Lanes Are Appropriate for Clover Hill Road
Clover Hill Road provides an important low-traffic bicycling connection between the City of Manassas (and adjacent residential neighborhoods within the County) and Manassas Regional Airport and points west, including the Broad Run VRE station and the new Route 28 shared-use path that now extends though Bristow all the way to Nokesville. On the southwest side of Route 234, Clover Hill Road provides critical bicycling access to a network of low-traffic, bicycling-friendly roads within and near Manassas Regional Airport, including Harry J Parrish Blvd. Wakeman Drive, Observation Drive, Piper Lane, Residency Road, Pennsylvania Avenue, Carolina Drive, and Gateway Blvd.
As such, Clover Hill Road is eminently useful for bicycle commuting to employment sites within and near the airport, to the Broad Run VRE station, and to points west in Bristow. In addition, Clover Hill Road and the low-traffic roads within and around the airport are used extensively for recreational bicycling on evenings and weekends.
Both City of Manassas roadways that connect to this segment of Clover Hill Road–i.e.. Clover Hill Road from Godwin Drive to Wellington Road and Godwin Drive from Clover Hill Road to Hastings Drive–already have conventional on-road bike lanes. Thus, in addition to including sidewalks for pedestrians, the entire redesigned segment of Clover Hill Road should include conventional on-road bike lanes in both directions.
Note that VDOT’s website that describes bowtie intersections includes conventional on-road bike lanes on all four legs of that intersection (see the illustration copied below).
Since, as in the above illustration, the proposed design features dedicated right-turn-only lanes on Clover Hill Road at both approaches to the Prince William Parkway, it would be vital to install the bike lanes at both approaches to the Prince William Parkway between the straight-through travel lane on the left and the right-turn-only lane at the curb.
Within the roundabouts, the bike lanes–if any–should be on the far right and could be buffered or physically separated from roadway traffic. Alternatively, especially if right-of-way is constrained at the roundabouts, the bike lanes could be discontinued within the roundabouts and bicyclists encouraged to navigate the roundabouts as either a driver centered within the travel lane or (using strategically placed curb ramps for access and egress) as a pedestrian using the sidewalk.
However, upon exiting each roundabout, right-turning motorists should be directed to yield to any bicycle traffic ahead and to carefully merge right across the continued bike lane to enter the emerging right-turn-only lane before reaching either the Parkway (along both southbound and northbound Clover Hill Road) or Godwin Drive (along northbound Clover Hill Road).
Please note that these same conflicts between right-turning motorists and straight-through bicyclists presently exist at the current Clover Hill Road/Route 234 Intersection in the absence of any bike lanes and that appropriate traffic engineering measures, involving pavement markings and signage, can optimize the safety of all road users.
Design This Intersection to Safely Accommodate the Future Shared-Use Path Along Route 234
Although this project won’t construct the long-planned missing shared-use path along Route 234, the design of this intersection should not preclude its future construction and should also ensure that pedestrians and bicyclists using that shared-use path can cross Clover Hill Road safely. As a designated segment of the National Capital Trail Network, a continuous, high-quality shared-use path along Route 234 should be a priority for Prince William County.
Unobstructed right-of-way should be acquired and preserved as part of this project to accommodate the future Route 234 shared-use path, and the project design should ensure that the route and future design of this path would not be blocked or compromised by noise barriers, above-ground or buried utilities, or roadside signage, traffic signals, or street lighting. Until the county decides whether this path will be constructed on the northeast or southwest side of Route 234, right-of-way should be reserved for the future shared-use path on both sides.
In addition, the intersection design should ensure that the future Route 234 Trail will have a safe, at-grade crossing of Clover Hill Road, presumably coordinated with the same traffic signal that regulates the Route 234 traffic.
Eliminate High-Speed Right-on-Red Turning Movements from Route 234 onto Clover Hill Road
Unlike VDOT’s model bowtie intersection illustrated above, the currently proposed intersection design incorporates two free-flowing, high-speed, right-turning movements, using pork-chop islands, for Route 234 traffic to enter Clover Hill Road. We believe this currently proposed design feature would seriously endanger both 1) bicyclists and pedestrians crossing Route 234 at Clover Hill Road and 2) the users of the future Route 234 Trail crossing Clover Hill Road.
Vulnerable, non-motorized road and trail users who are crossing either roadway on a green traffic signal should not be endangered by high-speed traffic that is simultaneously turning right-on-red at near-freeway speeds at these pork-chop islands. While a decision to completely ban all right-turn-on-red movements at this intersection might best be made by expert traffic engineers, we firmly believe that free-flowing right-on-red movements would be dangerous at this intersection and should not be promoted by design features such as pork-chop islands.
Instead, vehicle traffic entering Clover Hill Road from Route 234 should be encouraged to slow to the 25 MPH posted speed and carefully merge into the single travel lane approaching the roundabout, while bicyclists who have just crossed Route 234 on a green signal must merge into the bike lane at the right edge of the roadway.
Again, careful pavement marking and signing would help all road users safely negotiate these conflicts, whereas a design that promotes high-speed right-on-red vehicle traffic would endanger vulnerable road users.
Bicyclists and pedestrians crossing Route 234 at Clover Hill Road on a green traffic signal would primarily be endangered by motorists turning right-on-red from Route 234 at the far side of their crossing. By contrast, users of the future Route 234 Trail crossing Clover Hill Road on a green traffic signal could encounter both motorists turning right-on-green from Route 234 as well as motorists turning right-on-red from Clover Hill Road. All such right-turning movements would be safer if the design encourages motorists to slow or stop completely before entering a crosswalk and turning into the path of vulnerable road users. Partial traffic signal phasing, such as leading pedestrian intervals, could also make these crossings safer.
Clover Hill Road is a local street posted for 25 MPH, and there is no compelling need to promote free-flowing right-turn-on-red vehicle movements onto Clover Hill Road.
The 2019 AADT for all connected local roadways (i.e., Clover Hill Road, Godwin Drive, and Harry J Parrish Blvd) ranges from 2100 to 4700, so Clover Hill Road only needs one travel lane per direction between intersections. The proposed design includes a grassy median along Clover Hill Road, but there’s no compelling need for a grassy median on a road posted for 25 MPH, and that grassy median is about a full-lane wide on the segment approaching Godwin Dr.
Active Prince William also supports the inclusion of a shared-use path along this entire segment of Clover Hill Road; however, such a path would not connect to any existing path along Clover Hill Road, Godwin Drive or Harry J. Parrish Blvd, and it appears that the long-planned path along the Route 234 Bypass won’t be built for the foreseeable future. Thus, a shared-use path seems less essential, especially on the airport side of Route 234, provided that both sides of Clover Hill Road will have sidewalks and bike lanes.
If spatial or terrain constraints would otherwise preclude the addition of both on-road bike lanes and sidewalks along Clover Hill Road in both directions, consideration should be given to narrowing or eliminating the grassy medians.
Thank you for considering our input.