Evaluating Strategies for Work Zone Transportation Management Plans (2020) / Chapter Skim
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From page 57... ...
57 6.0 Field Evaluation of Temporary Ramp Metering Many regions have deployed, sustained, and expanded ramp metering to improve daytime traffic operations on freeways. It is a proven and efficient tool to address traffic congestion and safety issues; however, it is a challenge to use under work zone conditions.
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58 The northbound US 63 entrance loop at the point of merging with Highway 52 was allowed to form two lanes when merging. However, metering allowed only one car per green phase to merge onto the mainline.
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59 Figure 18. Ramp-metering data collection locations on MN Route 52 and Route 63 loop b ramp, Rochester, Minnesota.
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60 Figure 19. MnDOT ramp-control signal details.
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61 To evaluate the effectiveness of ramp metering in a work zone, Pennsylvania Department of Transportation (PennDOT) revised its approved MOT plans to include ramp metering at Union Avenue entrance ramp to southbound I-279.
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62 Figure 20. Ramp-metering data collection locations on I-279 and Union Avenue Ramp, Ohio Township, Pennsylvania.
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63 6.2. Study Methodology 6.2.1 Data Collection Duration MN Route 52, Rochester, Minnesota.
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64 • Vehicle speeds along mainline with and without ramp metering. Because the intent is that ramp metering will control the flow rate of vehicles entering the main line, this treatment may increase vehicle operating speeds on the mainline.
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65 6.2.6 Method for a Statistical Test for Frequency of Headway The statistical test for vehicle speeds is the same as described in Section 5.2.6. 6.2.7 Driver Compliance of Ramp Meter Signal This analysis is to determine the percentage of vehicles that complied with the ramp metering signal.
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66 Figure 21.
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67 The changes in the mean speeds and 85th percentile speeds for vehicles with and without rampmetering scenarios were calculated. Tables 24 and 25 show the comparison of mean speed and 85th percentile speed on the mainline and the statistical test results with and without ramp metering.
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68 Similar to the mean speeds, the 85th percentile speeds on the mainline of the freeway also increased for all time periods from 7:30 to 8:30 a.m. The t-test results indicated the increases in mean speed during the variable-cycle length ramp metering scenario were also statistically significant for all time periods.
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69 Figure 22.
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70 Figure 23.
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71 Figure 24. Hourly volume -- Location 3, after the merge area.
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72 Table 26. Speed comparison, meter-off scenario and fixed-cycle length ramp metering (right lane)
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73 Table 28. Speed comparison, meter-off scenario and variable-cycle length ramp metering (right lane)
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74 Figure 25. Vehicle speed -- Location 3: After the merge area.
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75 Overall, speeds increased in both right and left lanes, under the variable-cycle length ramp metering scenario by 57.2% (11.45 mph)
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76 Figure 26.
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77 The team used a comparison of travel times to evaluate the effect of ramp metering and determine if ramp metering caused changes in travel characteristics. The team used the tstatistic to evaluate the effect of different ramp-metering scenarios.
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78 6.4.1.1 Meter-off Scenario vs. Fixed-cycle Length Ramp Metering As Table 30 shows, the average travel time from Location 1 to Location 3 decreased for all time periods before 8:15 a.m.
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79 reduction) is the result of implementing ramp metering.
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80 Figure 27.
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81 Figure 28.
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82 The team used a comparison of travel times to evaluate the effect of ramp metering and determine if ramp metering caused changes in travel characteristics. The t-statistic was used to evaluate the effect of different ramp metering scenarios.
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83 Table 33. Travel time comparison, meter-off scenario and fixed-cycle length ramp metering (left lane)
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84 Table 34. Travel time comparison, meter-off scenario and variable-cycle length ramp metering (right lane)
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85 It can be reasonably concluded that the improved travel time (20% for fixed and 60% for variable) is the result of implementing ramp metering.
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86 6.5.1.2 Meter-off Scenario vs. Fixed-cycle Length Ramp Metering Figure 29 presents a visual performance comparison of headway distributions through a cumulative distribution function in the morning peak period at Location 3 for the meter-Off scenario and the fixed-cycle length ramp metering.
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87 6.5.1.3 Meter-off Scenario vs. Variable-cycle Length Ramp Metering Figure 30 presents a visual performance comparison of headway distributions through a cumulative distribution function in the morning peak period at Location 3 for the meter-off scenario and variable-cycle length ramp metering.
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88 The headways of vehicles on the mainline of the freeway at Location 3 showed an increase in both ramp-metering scenarios from meter-off scenario (without ramp metering)
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89 Meter-off Scenario vs. Fixed-cycle Length Ramp Metering (Right Lane)
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90 Meter-off Scenario vs. Variable-cycle Length Ramp Metering (Right Lane)
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91 6.5.2.2 Left Lane Table 38 summarizes the K-S test results of the meter-on scenarios for the left lane. The following discusses both Meter-on scenarios.
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92 Figure 33. Cumulative headway distribution plot, meter-off scenario vs.
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93 Meter-off Scenario vs. Variable-cycle Length Ramp Metering (Left Lane)
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94 statistically significant for three scenario comparisons (right lane, meter-off vs. variable-cycle length; left lane, meter-off vs.
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95 6.6. Network Summary Figure 35 provides a visual volume and speed graphic of the effect of ramp metering under meter off, fixed-cycle length, and variable-cycle length scenarios taken at the gore (mainline and ramp)
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96 Figure 36 illustrates the positive effect along the corridor before/after metering by operations. While both fixed-cycle length and variable-cycle length scenarios yielded positive results, the variable-cycle length scenario showed improved results with respect to vehicle speeds.
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97 6.7. Driver Compliance Rates The primary interest in evaluating the effectiveness of ramp metering is the drivers' compliance rate.
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98 6.8. Work Zone Crash Modification Factor for Ramp Metering This section discusses the CMF calculation for ramp metering in work zones.
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99 Table 40. CMF results for ramp meter.
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