Plotkin Ramp Meter Presentation Final

Report
GDOT’s Metro Atlanta
Ramp Meters
Marc Plotkin
Traffic Engineer II :Regional Traffic Operations
Topics
1.
2.
3.
4.
5.
6.
7.
8.
What, and Why
Safety
Benefits
Design Considerations
History in Atlanta
Implementation
Operations
Results and Findings
What Are Ramp Meters
• Part of NaviGAtor, Georgia DOT’s Intelligent Transportation System
(ITS)
•
“Traffic lights” on interstate entrance ramps designed to control
traffic flow onto the interstate
• Proven to relieve traffic congestion in over 20 U.S. cities for over 20
years
Ramp Meter Locations
Why?
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Reduces crashes at merge points
Increases freeway productivity
Reduces stop-and-go traffic
Reduces fuel consumption
Cost-effective traffic management tool
Improves trip predictability
Safety Analysis Minnesota
• Ramp Meter shutdown test
– With Metering 261 crashes
– Without metering 476
crashes
• Annual Savings from
metering
– Property damage only
• $4.8 million
– Injuries
• $6.8 million
– Fatalities
• $6.6 million
Reduction in Crashes
Portland, OR
Los Angeles, CA
43%
20%
Seattle, WA
38%
26%
Minneapolis, MN
Long Island, NY
15%
PREPARE
TO STOP
Benefits of Ramp Meters
• Improved traffic flow from
surface street to freeway
• Faster travel times
• Reduced merging accidents
• Reduced fuel consumption
• Reduced vehicle emissions
Design Considerations
•
Some ramps dropped out of consideration during design phase
•
No “geometrical” changes allowed
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Acceleration distances
– “slip” ramps – such as I-85 frontage road system
– Ramps with very short storage
– C/D ramps
– No widening
– Some striping changes allowed if shoulders maintained
– AASHTO Green Book compliance maintained
History of Ramp Meters in Atlanta
Begin Phase II –the Modern Years
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Preparation for Olympics in 1996
Congestion was back, relief needed and capacity was fixed
Pilot project – 5 ramps selected
Meters began operation December 1996
Low impact ramps were selected for the pilot:
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No widening/extending
Single lanes
Not a big residential area
Relatively low volumes
Downtown Atlanta 1967 – Atlanta History Center
Ramp Meter Pilot I-75 NB
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Meters programmed to turn ON at
3:45 PM weekdays (TMC Planning)
Loop Detection with 3 second gap
Max rate set on the fly
Minimize delay on ramp (adjust
rate)
Longer ramps = Adjust rate up
Shorter ramps = Adjust rate down
Meter ramps as needed on
individual basis
Base rates on various time of day
schedule
History of Ramp Meters in Atlanta
Phase III – the ‘Fast Forward’ years (2006-2012)
• GDOT elected to go “all in”
• Funding mechanism, Governors’ “Fast Forward” program
– 18 year worth of congestion-relief projects in 6 years
• Included 165 more ramp meters
• Staged installation, one freeway at a time
Meters on as of January 2009
GA 400
I-85
I-75
I-20
I-20
I-85
I-75
Meters on as of January 2010
GA 400
I-85
I-85
I-75
I-75
I-20
I-20
I-20
I-20
I-85
I-85
I-75
I-75
Georgia Ramp Meter System Today
GA 400
I-75
I-85
I-20
I-85
I-75
Current Ramp Meter Locations
• 185 Ramp Meters:
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Original 5 on I-75 NB, Midtown to Cumberland Mall (1996)
27 Locations on I-20
51 Locations on I-285
8 Locations on I-575
40 Locations on I-75 North and South of Atlanta
15 Locations on the 75/85 Connector
19 Locations on I-85
2 Locations on the Buford Connector
15 Locations on GA 400
8 Locations on US 78
Operations- GDOT Mindset
GDOT’s goal: partner with locals to provide the best possible travel time
for the public.
best = more consistent and reliable
Ramp meter’s objective: Aid the mainline while limiting the impact from
arterial networks supplying demand.
How do we do that?
• Providing consistent flow for merging vehicles
Resulting in improved
• Mobility
• Safety
Operations – Day to Day
Queue Management
• Making sure that arterials aren’t negatively impacted
How do we do that?
• Remote monitoring – during peaks
– Navigator 2
– Centrally connected system
• Threshold adjustments
– Speed up metering
– Shut down
• Ramp
• Mainline (Testing)
Queue Management
WITHOUT …
WITH …
Results
285 Westbound – PM peak – from Chamblee Dunwoody to I-75 (9 Miles)
Totals
Before
After
Change
Travel Time
(Min)
17.19
11.22
-5.97
Travel Time
reduced 6 Minutes
# of Stops
6.3
1.4
-4.9
Avg
Speed(mph)
33.9
51.9
18.0
Total
Delay(min)
5.62
1.02
-4.61
Results
285 Eastbound – PM peak from Roswell Rd to I-85 (8 Miles)
Totals
Before
After
Change
Travel Time
(Min)
16.12
11.45
-4.67
Travel Time
reduced 5 Minutes
# of Stops
6.3
1.4
-4.9
Avg
Speed(mph)
33.9
51.9
18.0
Total
Delay(min)
6.92
2.56
-4.36
Result Summary
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Travel time reductions ranged from:
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# of stop reductions ranged from:
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Total delay reductions ranged from:
– 50 seconds to 6 minutes
– 8 – 35%
– 0.7 to 5.3
– 30 seconds to 5 minutes
– 11 to 82%
Result Summary
•
Emissions data was also collected
– Hydrocarbon (g) reductions ranged from:

5 to 31%
– Oxides of Nitrogen (g) reductions ranged from:
 5 to 38%
 One corridor increased 6%
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Carbon Monoxide (g) reductions ranged from:
 1 to 15%
 Two corridors had increases (1% and 13%)
I-285 Westbound PM Peak
Thank you
Marc Plotkin
Traffic Engineer II
[email protected]

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