Month XX, 2004 Dr. Robert Bertini Using Archived Data to Measure Operational Benefits of ITS Investments: Ramp Meters Oregon Department of Transportation.
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Month XX, 2004 Dr. Robert Bertini Using Archived Data to Measure Operational Benefits of ITS Investments: Ramp Meters Oregon Department of Transportation
Presentation Outline Research Objectives What is Ramp Metering? Data Sources and Validation Analysis of Ramp Metering Case Study in Portland, Oregon Conclusions
Research Objectives Demonstrate the use and display of archived data from multiple sources as a tool for evaluation and monitoring of freeway operations. Evaluate the effectiveness of the ramp metering program in Portland, Oregon Develop tools to facilitate efficient deployment of ramp metering programs in Portland and other places
Transportation System Management 75 CCTV cameras 18 variable message signs 118 ramp meters 436 inductive loop detectors Digital archives of incident logs AVL Archives of COMET movements An extensive fiber optic communications system In the Portland metro area ODOT currently operates an extensive advanced traffic management system from the TMOC including:
What is Ramp Metering? Goals of Ramp Metering Limit the amount of traffic entering a freeway Break up the platoons of vehicles discharged from a traffic signal upstream. Picture
Benefits of Ramp Metering Improved traffic flow Reduction in travel time Improved safety Improved air quality The meters were shut down Minneapolis, Minnesota for eight weeks and a before and after analysis was performed. During the peak periods, freeway mainline throughput declined by an average of 14% with the ramp meters off and travel time increased by more than 25,000 (annualized) hours. In addition, crash frequency increased by 26% while the meters were off.
Data Sources Inductive Loop DetectorsClosed-Circuit Television Cameras Picture
Data Validation This study determined that loop detectors in the Portland region report an error code when no vehicles pass over a loop in the 20 second data interval. This makes it impossible to determine whether an error is indeed an error or just that there were no vehicles passing the loop in that given period. As a result of this study ODOT has updated the software to distinguish between data errors and zero counts, making future data easier to analyze. I- 5
Data Validation It was also determined that the loops count vehicles with 5 axles as two vehicles.
Ramp Meter Evaluation - Data Collection Probe Vehicles equipped with AVL systems made 6 runs along this corridor. Picture of Palm with ITS-GPS Loop detector data was archived at 20 second intervals for the same period of time.
Ramp Meter Evaluation - Conclusions Traffic data upstream of station 6 The most efficient choice for this section of freeway is to maintain flow below 6000 vph at a speed of 40 mph
Ramp Meter Evaluation - Conclusions First, we avoided reaching capacity on the freeway mainline. Second, we avoided reaching the spatial capacity of the on-ramps. Finally, we recommend that drivers be informed in advance about expected ramp delays and suggestions for possible alternate routes with the estimated travel time savings. Several points were considered when suggesting modifications the hypothetical ramp metering system timing plans:
Case Study:Portland, Oregon Ramp meters were first implemented in the Portland metropolitan area by ODOT in January 1981. ODOT currently maintains 118 ramp meters in the Portland metropolitan area, and all the meters are operated in a fixed- timed operation, activated and deactivated at the same times every weekday. ODOT’s goal is to maximize the capacity of the freeway while minimizing the effects on the arterial street system.
Weekend Shutdown In response to frequent weekend congestion on the eastbound lanes of Highway 26, ODOT implemented weekend ramp metering along an 11- mile corridor, between Helvetia Road and Skyline Road. In October 2003 these meters were deactivated for one weekend to evaluate the effectiveness of the weekend metering program.
Weekend Shutdown Ramp Metering led to a better quality of service throughout the corridor
Conclusions Transportation agencies around the world have experienced success with their ramp metering programs. Some have even seen freeway capacity above 2,000 vph per lane. Unfortunately, ramp meters are not a cure-all. While they can generate significant improvements in some areas, they cannot eliminate all congestion or every accident. The true measure of their effectiveness, however, is the continued increase in ramp metering implementations such as those demonstrated in cities such as Portland, Oregon.
Thank You U.S. Department of Transportation Transportation Northwest (TransNow) Oregon Department of Transportation Portland State University Department of Civil & Environmental Engineering Dennis Mitchell and Jack Marchant of ODOT Barnie Jones, Rob Edgar, Galen McGill and Edward Anderson at ODOT for their support The full report is available online at: http://www.its.pdx.edu/opbenefits.html Dr. Robert Bertini: email@example.com