STAFF REPORT
Operations Committee, April
30, 2008
Cary Parkway/High House Road
Intersection Study
(EN08-087)
Consideration of a request for funding to conduct a study on alternatives to
widening the intersection of Cary Parkway and High House Road
Speaker: Mr. David Spencer
From: Tim Bailey, PE, Director of Engineering
Prepared by: David Spencer, PE, Traffic Engineer
Approved by: William B. Coleman, Jr., Town Manager
Approved by: Benjamin T. Shivar, Assistant Town Manager
The intersection of Cary Parkway and High House Road is considered by many in the Town to be a centerpiece, signature intersection. The intersection design and landscaping treatments are considered ideal, pleasing, and similar features are desired at other major intersections throughout the Town. However, operationally, this intersection is not ideal.
The traffic volumes at this intersection are some of the highest in the Town (Annual Average Daily Traffic, AADT, for this intersection in 2005 was 47,500). The current geometrics contribute to the poor operation. For example, the lack of right-turn lanes reduces capacity by forcing through traffic and right-turn traffic to utilize the same lane. Current right-turn volumes on all approaches in the peak hour, with the exception of one, are well over 100 right-turn vehicles. With existing left-turn volumes at this intersection in excess of 300 vehicles in the peak hours and opposing volumes over 1,000 vehicles, dual left-turn lanes would reduce the extensive delays and queuing. Queue lengths are so long that they spill out into the through lanes, reducing the through capacity even further.
The current overall Level-of-Service (LOS) for the intersection is an E (71.6 seconds) in the AM peak hour and an F (99.9 seconds) in the PM peak hour. With the typical growth of ambient traffic, the overall LOS for this intersection is expected to fall to an F in both peak hours (80.2 seconds AM, 95.5 seconds PM). The addition of traffic from proposed developments in the vicinity is expected to increase delay and queuing even further. With the addition of these developments, average delay for the intersection is expected to reach over 104 seconds in the PM peak hour, with many movements experiencing delays of over 2 minutes. It should be noted that the LOS and delay reported here take into consideration the addition of right-turn lanes on two approaches; without these right-turn lanes, delay would be higher.
Maintaining the balance between aesthetics and operations is a challenging task. During the recent council retreat, the topic of providing improvements at this location was discussed. A study to analyze improvement scenarios that would improve capacity and safety without widening and/or significantly altering the aesthetics at this intersection should be undertaken.
Fiscal Impact: Staff estimates that contracting with an engineering consultant for a study to provide alternatives that don’t widen the intersection, analyze the resulting traffic volumes and congestion and provide a report that describes results and includes drawings and renderings of alternatives will cost $50,000.
Staff Recommendation: Staff recommends that $50,000 be appropriated from General Fund fund balance to the Engineering Department’s contracted services account.