Developing Measures of Effectiveness for Truck Weight Enforcement Activities Final Report (1998) / Chapter Skim
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APPENDIX C M.O.E. Field Evaluation of Candidate Measures
APPENDIX C M.O.E. Field Evaluation of Candidate Measures
Pages 129-156
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From page 129... ...
were based on their suitability to demonstrate truck weight enforcement effects. These measures addressed legal load-lim~t compliance objectives of truck weight enforcement procedures as well as Me potential for overweight trucks to produce pavement wear and tear.
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From page 130... ...
of the total ob Gross Weight Violation, Proportion served truck sample which exceeds the le gal gross weight limit. The extent to which average measured Gross Weight Violation, Severity gross weights for the observed sub-sample | of gross weight violators exceeds the legal gross weight limit.
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From page 131... ...
It is not possible to study validity, however, without inquiring into the nature and meaning of one's variables. The validity of the tested measures in this study was established based on weir relevance to truck weight enforcement objectives, i.e., examine compliance with legal weight limits (e.g., axle, axle-grouping, and gross weights)
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From page 132... ...
Both permanent weigh scale operations and portable roadside truck weighing procedures were observed as enforcement conditions. Results Candidate M.O.E.s were evaluated In this field study on the basis of matched WIM data sets representing controlled enforcement and nor-enforcement the periods.
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Table 2. California Measures Sensitivity Experiment Gross Weight Violation, Proportion Gross Weight Violation, Severity Single-axI~n Lion Single-axle Weight Violation, Severity Tandem-axle Weight Violation, Proportion Tandem-axle Weight Violation, Seventy Bndge Formula Violation, Proportion Bridge Formula Violation, Seventy Excess ESALs, Proportion Excess ESALs, Severity Note: Weight units are pounds 5.9% 2,567 2.9% 438 6.8% 2,016 44.3% 7,400 .
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From page 134... ...
when the scale was open. The presence of Bridge Formula violations was examined for both the baseline and enforcement conditions.
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sensitivity to the enforcement activity. The results confirmed the following M.O.E.s: Tandem-axIe Weight Violation Severity, Bridge Formula Violation Proportion, and Excess ESAL Severity.
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development. Although no promising difference was observed for average gross weight difference (e.g., gross weights exhibited a larger variance In the enforcement condition)
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- to a' ~ a)
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Georgia Measures Sensitivity Experiment Gross Weight Violation Proportion t _ Gross Weight Violation, Severity Steering Axle Weight Violation, Proportion Steering Axle Weight Violation, Severity Tandem Weight Violation, Proportion Tandem Weight Violation, Severity Bridge Formula Violation, Proportion Bridge Formula Violation, Severity Excess ESALs, Proportion . Excess ESALs, Severity Note: Weight units are pounds B-:- ease ins :: .....
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From page 139... ...
In general, the QC-corrected data set was more sensitive to ESAL variability differences between the baseline and enforcement conditions, and it detected lower third tandem weights during the enforcement condition. Moreover, the QC-corrected data set discerned Excess ESAL differences between baseline and enforcement conditions.
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The QC-corrected data set did discriminate between conditions, unfortunately noting larger gross weight violations during the enforcement period. The foregoing analysis concludes that it is generally recommended to conduct a QC check of WIM databases prior to application of an M.O.E.
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From page 141... ...
On that diate, Me Port of Entry was operated during both the Day and Swing shifts, thus allowing data comparison for Me corresponding period and traffic direction on April 7. The applied database for this enforcement-effects comparison consisted of 393 trucks for the baseline condition and 957 trucks for the enforcement condition, which were observed during equal time periods.
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.- .. Gross Weight Violation, Proportion Gross Weight Violation Severity S'ngle-axle Weight Violation, Proportion Single-axle Weight Violation, Severity Tandem-axle Weight Violation, Proportion Tandem-axle Weight Violation, Severity Bridge Formula Violation, Proportion Bridge Formula Violation, Severity Excess ESALs, Proportion Excess ESALs, Severity Note: Weight units are pounds 1 1 .2 °/0 ; 3,744 Ibs.
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exhibited Excess ESALs during the enforcement period. Moreover, this sub-sample exhibited lower average Excess ESALs than were observed for the baseline condition.
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Violation, Severity Tandem-axle Weight Violation, Proportion . Tandem-axle Weight Violation, Severity Bridge Formula Violation, Proportion Bridge Formula Violation, Severity ~ ~ Excess ESALs Proportion .
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~ I _ .. Bridge Formula Violation, Proportion Bridge Formula Violation, Severity Excess ESALs, Proportion E~E~ ~ _ Note: Weight units are pounds Appendix C 1 2.5 °/0 2,493 10.3 SO 6874 .
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From page 147... ...
A comparison of baseline versus enforcement conditions during three different weekdays produced a number of significant findings. While no day-of-week effects were readily evident to indicate on which days enforcement effort would more likely be effective, all of Me tested operational measures were shown to be sensitive to enforcement activity.
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Officials, we requested data sets representing designated study days during November, December, and January in order to support the Measures Sensitivity experimental design. However, November data were not provided due to problems with the WIM scale.
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From page 149... ...
BE -- - ~-~ - -- ~ Gross Weight Violation, Proportion Gross Weight Violation, Severity Single-axle Weight Violation, Proportion Single-axle Weight Violation, Severity Tandem-axle Weight Violation, Proportion Tandem-axie Weight Violation, Severity Bridge Formula Violation, Proportion Bridge Formula Violation, Severity Excess ESALs, Proportion Excess ESALs, Severity 1.55 °/0 2,O43 6.0 onto 1 ,338 7 2 onto 3,566 1 5o/o 2,200 9.1 3% .52 1.90 °/0 2,000 4.4 onto 1 ,231 8.3 onto 5,900 36 onto 1 ,700 10.70 °/0 .55 No No*
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Truck weights were marginally lower on average, 48,228 versus 50,646 during the enforcement period. During the enforcement period, the average overload violation was Appendix C 22
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From page 151... ...
The proportion of trucks exhibiting Excess ESALs, and their associated severity, while exhibiting tendencies to demonstrate valid enforcement effects, did not significantly differ between the enforcement and non-enforcement conditions. Generally smaller proportions of single-axle violations were observed during the enforcement condition, with the most pronounced difference being a reduction from 6.9 to 3.9 percent for the form axle.
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From page 152... ...
While generally weak M.O.E. validation findings were seen in Minnesota results, one data set did exhibit a smaller proportion of gross weight and tandem axle violations along with a tendency for less severe excess ESALs, and the other set produced a tendency to lower Bridge Formula violations.
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From page 153... ...
The results confirmed Me following M.O.E.s: Tandem-axte Weight Violation Severity, Bndge Formula Violation Proportion, and Excess ESAL Severity. Georgia Mobile truck-weight enforcement operations, utilizing an obtrusive portable roadside weigh scale, were conducted at a rural interstate location.
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From page 154... ...
validation findings were seen in Minnesota results, one data set did exhibit a smaller proportion of gross weight and tandem axle violations along with a tendency for less severe excess ESALs, and the other set produced a tendency to lower Bridge Formula violations. The results confirmed the following M.O.E.s: (1)
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l andem-axle Weight violation, Severity | ~| I ~l ridge Formula Violation, Proportion | ~| :' I Bridge Formula Violation, Severity | | ~I I . Excess ESALs, Proportion | ~| ~I ~ I Excess ESALs, Severity | ~| ~| ~l l Legend: 0= Significant elect; ~ = Non-significant tendency 27 Appendix C
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