Ramp Meters
Update
Overview
In an effort to alleviate congestion and emphasize motorist safety, the Georgia Department of Transportation continues to implement its ramp metering program. Ultimately, as many as 120 Atlanta-area interstate interchanges are expected to feature ramp meters by mid-2009.
Background
Ramp meters have been used effectively to reduce traffic congestion in more than 20 cities nationwide for more than 20 years. Recent studies show the effectiveness of ramp meters in reducing congestion, travel times and accidents.
Georgia DOT began implementing ramps meters on Interstate 75 in 1996 and continued the installation on I-75-85 Downtown.
Ramp Meters in Atlanta are necessary due to the increasing congestion in the metropolitan area. Georgia DOT’s 2004-2006 accident data shows approximately 9.5 percent of Atlanta's traffic accidents on I-75, I-85, I-20 and I-285 occurred at entrance ramps. These accidents were, in some way, related to merging onto the freeway.
What Are Ramp Meters?
Ramp Meters are traffic signal devices located on entrance ramps to the interstate. They regulate the frequency of vehicles entering the flow of traffic on a freeway.
Ramp Meters are one of the tools in the toolbox to help mitigate traffic congestion. By pacing the entry of vehicles onto the freeway – usually at 3 to 4 second intervals – the merging vehicles are less likely to slow the freeway traffic. The meters help to:
- Split up the continuous flow of traffic from entrance ramps
- Allow vehicles to merge with freeway traffic more smoothly
- Make travel safer
- Enable the freeway to accommodate more vehicles during peak hour travel
They are utilized during the morning/afternoon peak travel hours, Monday through Friday.
How Do Ramp Meters Work?
- Ramp meters work similarly to traffic signals with a red and green light. All vehicles must stop when the light is red.
- When the signal turns green, the vehicle at the front of the line on the ramp may cautiously move onto the freeway. Only one vehicle is allowed onto the freeway at each green light signal.
- Sensors are located at the top of each ramp to monitor back-ups that may occur on the ramps. If there are too many cars on the ramp, sensors alert the signal which then allow more cars onto the freeway. Operators at Georgia DOT's Transportation Management Center also will monitor the meters through cameras and will make necessary adjustments.
- On two lane ramps, the meters will allow one car to merge at a time.
Part of the Georgia DOT’s Intelligent Transportation System, the meters utilize an advanced camera system to determine the most effective operation of the meters. The ramp meters are controlled at the Georgia DOT’s Transportation Management Center by the NaviGAtor Intelligent Transportation System.
Benefits of Ramps Meters
- Reduce hours of vehicle travel
- Decrease fuel consumption
- Maintain consistent traffic flow on the interstate
- Allow more cars to use the freeway
- Increase freeway speeds
- Reduce some vehicle emissions
- Reduce rear-end and side swipe accidents – accidents associated with merging