Express lanes were analyzed in further detail in the following paragraphs. One-minute ETC volumes were calculated for each of the days and separated between the AM and PM time periods. Data from both the before study and after study were used. The one-minute volumes were used to calculate five-minute volumes. Tables 23 and 24 show the average five-minute volumes for each lane during the AM and PM time periods, respectively. Lanes are separated by whether they were the left or right lanes of that particular configuration. In addition, Figures 47 and 48 are graphical depictions of this data. During the AM before study time period, the right lane has higher volume. During the AM after study time period, the left lane has higher volume than the right. The same phenomenon is true for the volumes during the PM time periods.
Based on the graphs, we can see the differences between each particular lane. Note the shift in usage for the ETC lanes. The left lane in the before study has the lowest of the four volumes in each graph. This is the lane that required the most weaving in order for ETC customers to use.
Weaving was required upstream and downstream of the plaza in order to reach this lane and then maneuver back to the highway lanes, respectively. Notice that there is not as much of a difference between the volumes both ETC lanes in the after study. The left and right ETC lanes during the before study, on the other hand, have much different lane volumes.
Table 23 Analysis - Average Five-minute ETC Lane Volumes (AM)
AM (7:00 to 8:00)
Before Study After Study Time Interval Left Lane Right Lane Left Lane Right Lane
1 61 130 102 68
Table 24 Analysis - Average Five-minute ETC Lane Volumes (PM)
PM (5:00 to 6:00)
Before Study After Study Time Interval Left Lane Right Lane Left Lane Right Lane
1 55 134 124.5 77
5-min ETC Lane Volumes During the AM Period
Before Study - Left Lane Before Study - Right Lane After Study - Left Lane After Study - Right Lane
Figure 47 Analysis - Average Five-minute ETC Lane Volumes (AM)
5-min ETC Lane Volumes During the PM Period
0
Before Study - Left Lane Before Study - Right Lane After Study - Left Lane After Study - Right Lane
Figure 48 Analysis - Average Five-minute ETC Lane Volumes (PM)
A Chi-Square Test was performed on the 5-minute ETC volumes between days during the before study and days during the after study. The tests were separated by time period.
Statistics were calculated between each particular lane. The following summarizes the statistical test.
Null Hypothesis (Ho): the ETC lane volumes are not significantly different Alternative Hypothesis (Ha): the ETC lane volumes are significantly different
Results of the Chi-Square Test are included in Tables 25 and 26. Any results with a value less than 0.05 indicate that the mean difference is significant at the 0.05 level of significance. During the AM time period, although the right lane in the before Study is similar to the left lane in the after study, it is still significantly different since the p-value is less than 0.05.
During the PM time period, the right lane in the before study is not significantly different than the left lane in the after study, since it’s value is equal to 0.325 (greater than 0.05).
Table 25 Analysis - Chi-Square Test for ETC Lane Volumes (AM)
AM (7:00 to 8:00)
Before Study After Study Left Lane Right Lane Left Lane Right Lane Before Study Left Lane N/A 0.000 0.000 0.000 Right Lane 0.000 N/A 0.009 0.000 After Study Left Lane 0.000 0.009 N/A 0.000
Table 26 Analysis - Chi-Square Test for ETC Lane Volumes (PM)
PM (5:00 to 6:00)
Before Study After Study Left Lane Right Lane Left Lane Right Lane Before Study Left Lane N/A 0.000 0.000 0.000 Right Lane 0.000 N/A 0.325 0.000 After Study Left Lane 0.000 0.325 N/A 0.000 Right Lane 0.000 0.000 0.000 N/A
Overall averages were also calculated for the before study lanes and the after study lanes.
This gives an overall picture of the differences between the before study and the after study ETC volumes (average per lane). Figure 49 shows the trend that the after study volumes are generally higher than those in the before study for the ETC lanes. Figure 50 shows the slight differences between the before study and after study volumes during each five-minute increment. Note that the after study volumes are consistently equal to or higher than the before study volumes during the same time increments (five-minutes).
5-min ETC Lane Volumes (Before vs. After)
0 20 40 60 80 100 120 140
1 2 3 4 5 6 7 8 9 10 11 12
Time Interval
Average Throughput for All ETC Lanes
Before Study (avg) After Study (avg)
Figure 49 Analysis - Five-minute ETC Lane Volumes (Before Study vs. After Study)
5-min ETC Lane Volumes (Before vs. After)
40 60 80 100 120 140
for All ETC Lanes
Before Study (avg) After Study (avg)
A Scheffe’s statistical test was performed to determine the difference in speeds between the before study dedicated ETC lanes and the after study express ETC lanes. Table 27 is a summary of Scheffe’s test between the before study speeds and the after study speeds.
Null Hypothesis (Ho): the ETC lane speeds are not significantly different Alternative Hypothesis (Ha): the ETC lane speeds are significantly different
According to the results, there is a significant difference in speeds between each before study ETC lane and all of the after study ETC lanes.
Table 27 Analysis - Statistical Results for ETC Lane Speeds
Before Study (2002)