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GDOT’s Metro Atlanta Ramp Meters Marc Plotkin Traffic Engineer II :Regional Traffic Operations.

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Presentation on theme: "GDOT’s Metro Atlanta Ramp Meters Marc Plotkin Traffic Engineer II :Regional Traffic Operations."— Presentation transcript:

1 GDOT’s Metro Atlanta Ramp Meters Marc Plotkin Traffic Engineer II :Regional Traffic Operations

2 Topics 1.What, and Why 2.Safety 3.Benefits 4.Design Considerations 5.History in Atlanta 6.Implementation 7.Operations 8.Results and Findings

3 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

4 Ramp Meter Locations

5 Why? Reduces crashes at merge points Increases freeway productivity Reduces stop-and-go traffic Reduces fuel consumption Cost-effective traffic management tool Improves trip predictability

6 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

7 Reduction in Crashes Minneapolis, MN Los Angeles, CA Seattle, WA Portland, OR Long Island, NY 20% 43% 38% 26% 15%

8 Benefits of Ramp Meters Improved traffic flow from surface street to freeway Faster travel times Reduced merging accidents Reduced fuel consumption Reduced vehicle emissions PREPARE TO STOP

9 Design Considerations Some ramps dropped out of consideration during design phase – “slip” ramps – such as I-85 frontage road system – Ramps with very short storage – C/D ramps No “geometrical” changes allowed – No widening – Some striping changes allowed if shoulders maintained Acceleration distances – AASHTO Green Book compliance maintained

10 History of Ramp Meters in Atlanta Begin Phase II –the Modern Years 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: – No widening/extending – Single lanes – Not a big residential area – Relatively low volumes

11 Downtown Atlanta 1967 – Atlanta History Center

12 Ramp Meter Pilot I-75 NB 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

13 History of Ramp Meters in Atlanta Phase III – the ‘Fast Forward’ years ( ) 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

14 Meters on as of January 2009 I-20 I-85 I-75 GA 400 I-75

15 Meters on as of January 2010 I-20 I-85 I-75 GA 400 I-75 I-20 I-85 I-75 GA 400 I-75

16 Georgia Ramp Meter System Today I-75 I-20 I-75 I-85 GA 400

17 Current Ramp Meter Locations 185 Ramp Meters: Original 5 on I-75 NB, Midtown to Cumberland Mall (1996) 27 Locations on I Locations on I Locations on I 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 Locations on US 78

18 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

19 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)

20 Queue Management WITHOUT … WITH …

21 Results Travel Time (Min) # of Stops Avg Speed(mph) Total Delay(min) Totals Before After Change Travel Time reduced 6 Minutes 285 Westbound – PM peak – from Chamblee Dunwoody to I-75 (9 Miles)

22 Results Travel Time (Min) # of Stops Avg Speed(mph) Total Delay(min) Totals Before After Change Travel Time reduced 5 Minutes 285 Eastbound – PM peak from Roswell Rd to I-85 (8 Miles)

23 Result Summary Travel time reductions ranged from: – 50 seconds to 6 minutes – 8 – 35% # of stop reductions ranged from: – 0.7 to 5.3 Total delay reductions ranged from: – 30 seconds to 5 minutes – 11 to 82%

24 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% Carbon Monoxide (g) reductions ranged from:  1 to 15%  Two corridors had increases (1% and 13%)

25 I-285 Westbound PM Peak

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29 Thank you Marc Plotkin Traffic Engineer II


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