Evaluating Strategies for Work Zone Transportation Management Plans (2020) / Chapter Skim
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100 7.0 Field Evaluation of Reversible Lanes A reversible lane is one in which the direction of traffic flow in one or more lanes is changed to the opposite direction for some period of time. Its utility is derived by taking advantage of the unused capacity of the minor flow direction to increase capacity in the major flow direction, thereby negating the need to construct additional lanes.
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101 The bridge replacements and road reconstruction started in March 2015, and ended in November 2016. The team collected data from June 28 to July 12, 2016, when average daily traffic peaked because of the holiday period.
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102 occurred daily -- morning peak period to afternoon peak period between noon and 2:00 p.m., with the other changeover occurring after 8:.00 p.m. for the next day's morning peak period.
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103 7/8/2017 Saturday 3 2 11:00 a.m. 7/12/2017 Wednesday 2 3 10:30 a.m.
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104 measures of flow passing a point. To some extent, the minimum acceptable mean headway determines the roadway capacity.
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105 Figure 38. Data collection locations.
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106 Figure 39. I-75 daily traffic volumes (with reversible-lane change times)
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107 Figure 40. I-75 hourly traffic volumes (with reversible-lane change times)
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108 Figures 41 and 42 illustrate the vehicle speeds and traffic volumes on the mainline for northbound direction and southbound direction, respectively. The graphs indicated that I-75 did not have daily peaks; rather, a peak period that spans the entire day from about 10:00 a.m.
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109 Figure 41. Northbound average speed and traffic volumes (10:00 a.m.
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110 Figure 42. Southbound average speed and traffic volumes (10:00 a.m.
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111 7.3.1.2 Statistical Analysis of Vehicle Speed The team calculated changes in the mean speeds and 85th percentile speeds for vehicles between with and without implementation of the reversible lane. Tables 43 and 44 show the comparison of mean speed and 85th percentile speed of vehicles on the mainline of the freeway and the statistical test results with and without the implementation of the reversible lane.
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112 As Table 44 shows, the southbound mean speeds of vehicles on the mainline of the freeway increased for all time periods from 10:00 a.m.
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113 7.3.1.3 Comparison of Results for Travel Time Comparing travel times through the work zone is a good measurement of effectiveness to determine the effect of implementing the reversible lane. The reversible-lane operation maintains capacity through the work zone and is expected to have no effect on vehicle speeds, which will result in similar travel times to the baseline.
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114 Figure 43. Northbound travel time (distance: 6.5 mi)
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115 Figure 44. Southbound travel time (distance: 6.5 mi)
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116 7.3.1.4 Statistical Analysis of Travel Time Tables 45 and 46 show the comparison of average travel time with and without the reversible lane. As Table 45 shows, the NB average travel time through the project limits was maintained or lower with the reversible-lane operation -- except during the late afternoon when traffic volumes increased by 20% to 30%.
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117 Table 46. Travel time comparison -- southbound direction baseline location vs.
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118 As mentioned above, the team used the K-S test to judge how faithfully a distribution fits the sample data. The team adopted the K-S test to determine the goodness-of-fit in the work zone traffic condition.
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119 Figure 45. Cumulative headway distribution plot -- northbound peak direction period -- baseline location vs.
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120 Table 48 summarizes the K-S test results of the southbound peak direction vs. reversible-lane location.
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121 Figure 46. Cumulative headway distribution plot -- southbound peak direction period -- baseline location vs.
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122 7.3.2 Location: I-94, Maplewood, Minnesota 7.3.2.1 Comparison of Results for Vehicle Speeds The team collected data at four locations on I-94 -- two within the work zone (in the reversiblelane configuration) and one each upstream and downstream (outside the work zone)
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123 Figure 47. Data collection locations.
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124 Figure 48. I-94 hourly traffic volumes.
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125 Figures 49 and 50 illustrate the vehicle speeds and traffic volumes on the mainline for the a.m. peak westbound direction and the p.m.
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126 Figure 49.
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127 Figure 50.
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128 7.3.2.2 Statistical Analysis of Vehicle Speed The team calculated changes in the mean speeds and 85th percentile speeds for vehicles between with and without implementation of the reversible lane. Tables 49 and 50 show the comparison of mean speed and 85th percentile speed of vehicles on the mainline of the freeway and the statistical test results with and without implementation of the reversible lane.
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129 Table 50. Speed comparison -- (p.m.
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130 Figure 51.
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131 Figure 52.
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132 7.3.2.4 Statistical Analysis of Travel Time The team used a comparison of travel times to evaluate the effect of the reversible lane and determine if the reversible lane caused changes in travel characteristics. The team used the tstatistic to evaluate the effect of implementing the reversible-lane condition.
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133 Table 52. Travel time comparison -- (p.m.
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134 Table 53. K-S test results for the a.m.
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135 Figure 53. Cumulative headway distribution plot -- (a.m.
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136 critical value of 0.05) , which suggests the differences in the two cumulative distributions are statistically significant.
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137 7.3.3 Location: I-75 and I-675, Saginaw and Bay Counties, Michigan 7.3.3.1 Comparison of Results for Vehicle Speeds The team collected data at four locations on I-75 -- two within the work zone (in the reversiblelane configuration) and one each upstream and downstream (outside the work zone)
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138 Figure 55. Data collection locations.
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139 Figure 56. I-75 daily traffic volumes.
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140 Figure 57. I-75 hourly traffic volumes.
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141 Figures 58 and 59 illustrate the vehicle speeds and traffic volumes on the mainline for the northbound and southbound directions, respectively. The graphs indicated that I-75 did not have daily peaks; rather, a peak period spans the entire day from about 10:00 a.m.
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142 Figure 58. Northbound average speed and traffic volumes.
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143 Figure 59. Southbound average speed and traffic volumes.
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144 7.3.3.2 Statistical Analysis of Vehicle Speed The team calculated changes in the mean speeds and 85th percentile speeds for vehicles between with and without implementing the reversible lane. Tables 55 and 56 show the comparison of mean speed and 85th percentile speed of vehicles on the freeway mainline and the statistical test results with and without the implementation of the reversible lane.
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145 Table 56. Speed comparison -- southbound direction baseline location vs.
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146 Figure 60. Northbound average travel time (distance: 7.3 mi)
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147 Figure 61. Southbound average travel time (distance: 7.3 mi)
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148 7.3.3.4 Statistical Analysis of Travel Time The team used a comparison of travel times to evaluate the effect of the reversible lane and determine if the reversible lane caused changes in travel characteristics. The team employed the t-statistic to evaluate the effect of implementing the reversible lane.
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149 Table 58. Travel time comparison -- southbound direction baseline location vs.
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150 Table 59. K-S test results for the northbound peak direction period.
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151 Table 60 summarizes the K-S test results of the southbound peak direction vs. reversible- lane location.
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152 Figure 63. Cumulative headway distribution plot -- southbound peak direction period -- baseline location vs.
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153 increase the directional capacity, regardless of whether it supports daily (commuting) or weekday (holiday/recreational)
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154 Figure 65. I-75 and I-675 in Saginaw and Bay Counties, Michigan, speed-flow plots.
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155 Figure 66. I-94 in Maplewood, Minnesota, speed-flow plots.
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156 7.5. Work Zone Crash Modification Factor for Reversible Lane Table 61 shows the expected and actual crash results for deploying a reversible lane.
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157 Table 62. CMF results for reversible lane.
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