A ramp metering system controls the rate of vehicles entering the freeway from an entrance ramp. This system uses either a 3-section (red-yellow-green) ramp metering signal or a 2-section (red-green) signal to direct motorists to either stop before entering the freeway or continue entering the freeway. The signals can be set for different metering rates to reduce congestion and maximize freeway flow. The ramp metering signal is either located to the drivers’ left or on both sides on a single lane ramp. Ramp metering signals are, however, located on both sides on a two lane ramp.
Ramp metering system can be used in any type of ramp. Many types of ramp metering systems could be used, some of which are:
- Single lane one car on green light
- Single lane multiple cars on green light
- Multiple lane multiple cars on green light
The Portable Ramp Metering System (PRMS) is a portable, automated, real-time traffic information system that monitors traffic congestion both on the freeway and the ramp. This system directs motorists preparing to merge on the freeway, to either stop before entering the freeway or continue on the ramp leading to the freeway. PRMS uses portable ramp metering signals to direct the motorists. PRMS uses signal timing algorithms and real-time data from non-intrusive sensors to calculate metering rates. The sensors placed on the ramp are used for queue, check-in and check-out detections. The queue detection sensor is used to hold back overflow of vehicles on the surface road. Additional sensor may be used for merge detection. On the freeway, the sensors are placed either upstream and downstream of the ramp or placed only on the upstream of the ramp. The number and placement of the sensors depend upon the geometry of the ramp and is determined by the type of algorithm used by the ramp metering system.
- Can be integrated with advance warning signs with flashing beacons or changeable message signs indicating that ramp metering is active.
- Can be integrated with cameras that can bring live pictures of the highway to the internet.
- Can allow remote control of the system from anywhere.
Major Components of PRMS:
- Wireless communication
- Software with intelligent traffic algorithm
- Mobile solar-powered trailers
- Portable ramp metering signals
Expected Benefits of PRMS:
- Increases throughput and operating speeds in the freeway
- Reduces delay and travel time
- Better informs motorists and reduces their frustrations
- Makes freeway safer for motorists
- Reduces accident rates