Evaluating Strategies for Work Zone Transportation Management Plans (2020) / Chapter Skim
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21 5.0 Field Evaluation of Truck Lane Restrictions A large volume of trucks can degrade the speed, comfort, and convenience of passenger car drivers sharing the road. This problem is exacerbated in work zones that may operate at a reduced capacity or reduced operating speeds resulting from lane closures, lane-width reductions, geometrics, etc.
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22 static sign was placed ½-mi upstream from the beginning of the taper, second static sign was placed 2 mi downstream of the taper, and the last static sign was placed a further 2 mi downstream of the second static sign. The message on the static signs and the PCMS was the same (TRUCKS USE LEFT LANE)
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23 5.2. Study Methodology 5.2.1 Data Collection Duration I-75, Monroe County, Michigan.
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24 • Frequency of headway. Vehicle headway is a measure of the temporal space between two vehicles, and is defined as the elapsed time between the arrival of the leading vehicle and the following vehicle at a designated test point.
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25 Equation 2. Combined proportion of vehicles during the before-after data collection periods.
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26 The degrees of freedom (df) for the independent samples t-statistic is nA + nB - 2.
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27 A smaller K-S statistic value indicates a better goodness-of-fit, and in a two-sample K-S test, the decision to reject the null hypothesis is based on comparing the p-value with the significance level α.
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28 Figure 3 shows the differences in the percentage of trucks using the right and the left lane in the without and with conditions during the morning peak period (6–9 a.m.) at the SB I-75 test site.
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29 Figure 4. SB I-75 Comparison of truck lane distribution during mid-day period (10 a.m.–1 p.m.)
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30 5.3.2 SB US-23 Location Table 4 and Figures 6 through 8 show the lane distributions of trucks in percentages without and with the truck lane restrictions. When the truck lane restrictions were implemented, the percentage of trucks in the left lane increased for all time periods.
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31 Figure 6. SB US-23 comparison of truck lane distribution during morning peak period (6–9 a.m.)
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32 Figure 8 shows the differences in the percentage of trucks using the right and the left lane in the without and with conditions during the evening peak period (3–6 p.m.) at the SB US-23 test site.
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33 Table 5. NB US-23 Differences in lane distribution without and with truck lane restrictions.
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34 without truck lane restrictions to 21.5 percent with the truck lane restrictions, an increase of 726.9 percent. During the same time period, the percentage of trucks using the right lane decreased from 19.5 percent without truck lane restrictions to 9.3 percent with the truck lane restrictions, a decrease of 52.3 percent.
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35 Figure 11. NB US-23 Comparison of truck lane distribution during evening peak period (3–6 p.m.)
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36 Table 6. Lane distribution differences without and with truck lane restrictions for all sites.
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37 5.4. Comparison of Results for Truck Speeds A comparison of truck speeds was conducted to evaluate the effect of lane-use restriction.
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38 With the truck restrictions in place, the passenger car average speeds increased in the left lane during the morning peak period (by 8.82%) , mid-day period (by 5.43%)
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39 Table 10 shows the comparison of average speed of passenger cars without and with the truck lane restrictions. With the truck restrictions in place, the passenger car average speeds increased slightly in the right lane during the morning peak period (by 1.11%)
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40 Table 11. NB US-23 truck speeds without and with truck lane restrictions.
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41 Car–truck interactions are viewed as the driving actions of non-truck drivers resulting from psychological discomfort in the vicinity of trucks, primarily due to truck physical/operational characteristics. While interactions can also arise from the truck driver perspective, they tend to be less significant behaviorally as cars are smaller in size and have better operational characteristics.
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42 the without condition as opposed to 286 ft during the with condition. With the significance level α of 0.05 and the sample size of 2,254 for the without condition and 2,730 for the with condition, the critical statistic of K-S test for the maximum difference between the cumulative distributions, D, was 0.04.
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43 SB I-75 Headway Analysis Results Using K-S Test -- Right Lane Figure 13 presents a visual performance comparison of headway distribution through a cumulative distribution function in the morning peak period for the without condition vs. the with condition in the right lane.
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44 Figure 13. SB I-75 Cumulative headway distribution plot (right lane)
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45 test for the maximum difference between the cumulative distributions, D, was 0.04. The results of the K-S test for the without condition vs.
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46 Figure 15 presents a visual performance comparison of headway distributions through cumulative distribution function in the morning peak period for the without condition vs. the with condition on the SB right lane.
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47 Figure 15. SB US-23 Cumulative headway distribution plot (right lane)
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48 5.5.1.3 NB US -23 Tables 17 and 18 summarize the K-S test results of without and with implementation of truck lane restrictions. A discussion of the headway analysis comparison for the right lane and left lane follows.
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49 Figure 16. NB US-23 Cumulative headway distribution plot (left lane)
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50 NB US-23 Headway Analysis Results Using K-S Test -- Right Lane Figure 17 presents a visual performance comparison of headway distribution through cumulative distribution function in the morning peak period for the without condition vs. the with condition on NB right lane.
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51 Figure 17. NB US-23 Cumulative headway distribution plot (right lane)
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52 mean gaps in the left lane decreased for C-C (by 4.5%)
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53 Table 19. SB I-75 Platoon headways and gap acceptance (3–6 p.m.)
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54 Table 21. NB US-23 Platoon headways and gap acceptance (3–6 p.m.)
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55 5.6. Work Zone Crash Modification Factor for Truck Lane Restrictions This section discusses the CMF calculation for deploying truck lanes.
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56 Table 23. CMF results for truck lane restriction.
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