Post on 13-Apr-2017
OR126/Tom McCall
Intersection Improvements
August 2, 2016
Traffic Engineering Analysis
Operational Analysis– Utilize Highway Capacity Manual
• Volume-to-capacity ratio• Delay• Level-of-service• Queues
Safety Analysis– Utilize Highway Safety Manual and supplementing research
• Crashes per year• Severity
Existing Intersection Operations
Existing Intersection Safety Performance
5 years of historical crash data– Total Number of Crashes: 12– Total Injuries: 12
How does a roundabout compare to a signal?Year 2035 Operations – Average Delay per Vehicle
> 80s
~ 29s (With left-turn lanes)
29s (Single-lane roundabout)24s (With NB right-turn lane)
OR126/Tom McCall
Vehicle stackingQueues are approximately half as
long with roundabout vs. signal
How does a roundabout compare to a signal?Future Safety Performance over 5 Years
6.5 Total Crashes 3.4 Fatal/Injury
3.6 Total Crashes 3.3 Fatal/Injury
1.9 Total Crashes 0.4 Fatal/Injury
71% reduction87% reduction
OR126/Tom McCall
44% reduction3% reduction
Questions?
73’
130’
112’
113’
73’
Roundabouts reduce crashes
Over 90% reduction in fatalities 76% reduction in injuries 35% reduction in total crashes
* NCHRP Report 572
Pho
to: L
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Safety Performance (NCHRP Report 572)
78% reduction in injuries 48% reduction in total crashes
CONVERTED TO