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RIVERTON CITY ROUNDABOUT TUCKETT & FERGUSON CONSULTING
CE EN 472 – Senior Design
JOSH BELNAP TYSON FERGUSON PETE KELLY ROB NAYLOR BEN TUCKETT WINTER 2012
• Objectives
• Project Site
• Design Concept/Components
• Cost Analysis
• Traffic Analysis
• Summary
• Examine feasibility of a roundabout in Riverton, Utah
• Create a roundabout design to meet future traffic demands
Project Site PROJECT SITE
Design Concept DESIGN CONCEPT
Two Lane vs One Lane With Slip Lane
Safety
• Fewer Collision Points
• No Weaving Movements
Efficiency
• No yielding required on slip-lane
• Fewer cars in roundabout
ADVANTAGES OVER TWO LANE ALTERNATIVE
Signs
1st 2nd 3rd
SIGNING
Other benefits include:
• Fewer Collisions
• Less delay per vehicle
• Less vehicular emissions
Roundabout Signal
Cost of Construction 700,000$ 700,000$
Cost of Maintenance per year 2,000$ 5,000$
Lifetime savings 90,000$ -$
COST ANALYSIS
Objective - Design a roundabout to serve traffic conditions in 2030 at a Level of Service (LOS) C
Assumptions
• 50/50 directional split
• K-factor from 8% to 12%
• 10% heavy-vehicle factor
• 180 pedestrians/hour (Synchro)
• 100 pedestrians/hour (HCM)
• Peak hour factor of 0.92
TRAFFIC ANALYSIS
Results
• A k-factor > 10% causes excessive queuing
• More vehicles on slip lanes decreases overall delay
SYNCHRO
K = 8% K = 12%
Results
• LOS measured by vehicle delay
• Delay increases with more vehicles in the circulatory roadway
• LOS worsens as k-factor increases
• LOS C at k = 0.10
• Additional traffic control devices are recommended if delay exceeds 35 seconds per vehicle
HIGHWAY CAPACITY MANUAL LOS
An effective alternative should future traffic conditions reach LOS F
METERING
SUMMARY
• Reduced delay and maintenance costs compared to signalized alternative
• Safer than traditional two lane roundabout alternative
• User friendly and easy to navigate
• Questions?