WATSON AVENUE Frequently Asked Questions

Q: Why is the Town constructing a roundabout at the Park Avenue (SH 9)/Watson Ave ? A: A 2017 roundabout feasibility study confirmed that the intersection of Park Avenue (SH 9) and Watson Ave met the criteria for a signal, but that a roundabout would better serve the needs of the location. Another preliminary traffic study determined the intersection currently operates at a Level of Service F, meaning drivers see excessive delays and poor travel times, and the intersection exceeds the amount of vehicles that can be accommodated. Additionally, the construction of the parking structure on the South Gondola Lot will add 425 additional parking spaces, which will add more demand to necessitate the construction of improvements at this intersection.

Q: How does a roundabout intersection compare to a signalized intersection? A: There are many differences between these two types of intersections from a safety, traffic operations, economic, environmental and aesthetics standpoint. More specifics are provided below:

Safety Benefits When comparing to signalized intersections with regard to safety, roundabouts have a clear advantage based on many studies, especially regarding fatal and injury crashes. Roundabouts reduced injury crashes by 75 percent at intersections where stop signs or signals were previously used for traffic control, according to a study by the Insurance Institute for Safety (IIHS). Roundabouts benefit from good geometry, exhibiting only a fraction of the troublesome crash patterns typical of right-angle intersections. A typical four-legged intersection has 32 vehicle-to-vehicle conflict points and 24 vehicle-to-pedestrian conflict points. By comparison, a four-legged roundabout has only eight vehicle-to-vehicle conflict points and eight vehicle-to-pedestrian conflict points. This is an approximate 70 percent reduction in conflict points.

Within a roundabout, vehicles travel in the same direction, eliminating the right-angle and left-turn conflicts associated with traditional signalized intersections while providing positive speed control through geometric features and not relying on motorist to obey traffic control devices. entering a roundabout are gently curved to direct drivers into the intersection and help them travel counterclockwise around the roundabout.

With lower speeds, this provides more time for entering drivers to judge, respond and adjust speed, and enter a gap in circulating traffic. Speeds in the roundabout are typically between 15 and 20 miles per hour. The few collisions that occur in roundabouts are typically minor and cause few injuries since they occur at such low speeds. Because traffic is constantly flowing through the intersection, drivers do not have the incentive to speed up to try and "beat the light," like they might at a traditional signalized intersection.

Traffic Operations and Flow Benefits Roundabouts are designed to promote a continuous, circular flow of traffic. Drivers need only yield to traffic before entering a roundabout; if there is no traffic in the roundabout, drivers are not required to stop. Roundabouts typically operate with lower vehicle delays than other intersection control types.

When there are queues on one or more approaches, traffic within the queues usually continues to move, and this is typically more tolerable to drivers than a stopped or standing queue. The performance of roundabouts during off-peak periods is particularly good compared with other intersection forms, usually with very low average delays. A roundabout typically outperforms a signal in terms of reduced delay and shorter queues, it will require less queue storage space on the approach legs. As a result, roundabouts may reduce the need for additional right-of-way on the links between intersections, at the expense of additional right-of-way requirements at the intersections themselves. It may also be possible to space roundabouts closer together than traffic signals because of shorter queue lengths.

Economic Benefits The cost difference between building a roundabout and a traffic signal is comparable. Where long-term costs are considered, roundabouts eliminate hardware, maintenance and electrical costs associated with traffic signals, which can cost between $5,000 and $10,000 per year. Roundabouts are also more effective during power outages. Unlike traditional signalized intersections, which must be treated as a four-way stop or require police to direct traffic, roundabouts continue to work like normal.

Environmental Benefits Vehicles entering a roundabout must yield at entry, but are not required to stop if the roundabout is clear. This eliminates some stop-and-go traffic associated with stop sign or traffic signal-controlled intersections. This leads to fewer vehicles idling while stopped at an intersection leading to air quality concerns.

Aesthetic Benefits Roundabouts offer an opportunity to provide landscaping and urban design to provide an attractive corridor for all users and allow for gateway features and provide a sense of place and community character. Whereas signalized intersections have limited opportunities to provide aesthetic improvements.

Sources: FHWA NCHRP Report 672, Washington State DOT, and Iowa DOT

Q: Why is the Town not widening Park Avenue (SH 9) with this project? A: Park Avenue (SH 9) is a CDOT highway and is planned to be widened through a future project through CDOT.

Q: How do the transit center improvements relate to the Watson Avenue roundabout project? A: The project team working on the Watson Avenue roundabout is also coordinating with the transit center design to provide a cohesive set of improvements for the area. The final design of the Watson Avenue roundabout will accommodate all modes including the transit traffic from the transit center.

Q: Are pedestrian crosswalks and included in the Watson Avenue roundabout project? A: Sidewalks are planned for the east side of the roundabout and will connect to the Blue River Rec Path on Watson Avenue. Currently, a is not planned for the west side of the roundabout. Pedestrians on the west side of Park Avenue (SH 9) will be directed to cross Park Avenue (SH 9) using the existing pedestrian underpass or at the Ski Hill intersection. Since sidewalks will not be constructed on the west side of the roundabout, crosswalks across Park Avenue (SH 9) will not be needed at the roundabout, which will reduce vehicle and pedestrian conflicts.

Q: Why is a two roundabout being designed for a single lane road? How will the two lane roundabout merge back into a single lane road and will the merge point cause traffic congestion into the roundabout? A: A preliminary traffic analysis reviewed traffic conditions in 2040 and determined that a single lane roundabout would perform at a poor level of service in 2040. A two lane roundabout provides additional turning movements and capacity to improve the level of service. The merge points to a single lane on Park Avenue (SH 9) are being analyzed and designed to terminate at a sufficient distance away from the roundabout to prevent traffic from queuing into the roundabout. The two lane roundabout will result in shorter queue lengths and vehicle delays than a single lane roundabout.