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https://www.nationalacademies.org/trb/events

Measuring the Effectiveness of Ramp Metering Strategies on I-12

Ramp metering is one of the successful traffic control strategies in the area of active traffic and demand management. This study evaluates the effectiveness of a fixed time ramp metering control on the day to day operation of traffic over two segments of I-12, seven miles apart, in Baton Rouge, LA. Traffic data were collected and analyzed using MIST (Management Information System for Transportation) detectors at one segment, and DCMS (Data Collection and Management Service) detectors at the other segment. The assessments undertaken include a comparative speed analysis, travel time savings analysis, level of service analysis, and speed contours analysis of the conditions before and after deployment of the ramp metering. For the MIST segment, the statistical analysis showed that for the eastbound evening (PM) peak period, 47% of the time there were significant speed increases of 7 mph, but 12% of the time there were significant speed decreases of 17 mph. For the westbound morning (AM) peak period, significant speed increase of 5 mph were observed 43% of the time while significant speed decrease of 7 mph were observed 29% of the time. The speed contours analysis supported these findings with more areas of congestion observed in the westbound AM peak period than was observed in the eastbound PM peak period. The travel time analysis showed mixed results of reduced and increased travel times depending on which weekday was being analyzed. The level of service results suggests an overall deterioration of traffic conditions for both peak periods. For the DCMS segment, however, there was an average decrease in speed from 61.91 to 58.37 mph for the eastbound PM and 53.78 to 49.06 mph for the westbound AM peak periods. The speed contours showed increased areas of congestion for both peak time periods, and analysis of travel time savings showed overall increases in travel times for both peak periods. The level of service results supported the findings, showing worsened level of service (LOS) distributions for both peak periods. It should be noted, however, that the analysis for the DCMS segment did not account for the effect of the on-going construction work between O’Neal Lane interchange and Walker/La. 447 interchange, which started as early as 2009. It is possible that the presence of the construction zone may have impacted the traffic conditions and obscured the benefits of ramp meters. This is because the construction work schedule overlapped with the analysis time period. For both segments, it was not possible to isolate the effect of incidents on traffic conditions when measuring the performance of ramp meters since incident logs were not available at the time the analysis was done. While the fixed time operation of the ramp metering system on I-12 was effective to some extent on one of the western segment of I-12, the study recommended further investigation to determine if other ramp metering strategies would be more effective. This includes both local and coordinated demand responsive ramp metering systems. Furthermore, due to the confounding effect of the work zone in the eastern segment of I-12 and the current fixed time ramp metering system, the study recommended further comparative analysis by turning the ramp meters on and off for a few days to determine the effect on traffic conditions. This practice was followed in other studies such as the one in Minnesota.

Language

  • English

Media Info

  • Media Type: Digital/other
  • Edition: Final Report
  • Features: Appendices; Figures; Maps; References; Tables;
  • Pagination: 233p

Subject/Index Terms

Filing Info

  • Accession Number: 01501945
  • Record Type: Publication
  • Report/Paper Numbers: FHWA/LA.08/507
  • Contract Numbers: LTRC Project No. 11-2SS; State Project No. 3000017
  • Files: TRIS, ATRI, USDOT, STATEDOT
  • Created Date: Dec 23 2013 7:53AM