Developing Measures of Effectiveness for Truck Weight Enforcement Activities Final Report (1998) / Chapter Skim
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4.0 M.O.E. USER GUIDE
4.0 M.O.E. USER GUIDE
Pages 10-39
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Guidelines are applied to estimate the number of WIM data collection sites and required sample sizes required to measure an enforcement effect. This guideline provides users with estimates for specified roadway classification and truck percentage conditions.
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Sampling guidelines are directed toward WIM database gathering. It must also be emphasized that the soundness of the WIM input data and its subsequent analysis to measure the effectiveness of truck weight enforcement is highly dependent on calibration and maintenance of that equipment.
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4.~.~. Sampling Observation Levels Separate observation levels for sampling truck-weight violations were devised in order to meet the diverse evaluation requirements of varied truck weight enforcement operations.
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WIM Data Site Number Requirements Guidelines for determining the required number of observation sites for a statew~de/regional study of truck weight enforcement e~ectiveness were determined on the basis of observed M.O.E. distributions2 from representative See Appendix F
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Minimum Site-number Guideline for Selected M.O.E.s in State/Regional Truck Weight Enforcement Evaluations Rural Interstate < 15 % Trucks 15to30% Trucks , , > 30% Trucks Rural Primary Arterial < 9 TO Trucks 9 to 30 % Trucks l l > 30% Trucks Rural Minor Arterial Urban Interstate < 9% Trucks .
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of interest to be the "Proportion of Gross Weight Violations", then the number of required sites for each highway category watt be denved from numbers shown in the left-most column of Table 2. That is, at least three data collection sites are required to represent Rural Interstates with less Man ~ 5 percent trucks, six to represent Rural Interstate s with ~ 5 to 30 percent trucks, etc.
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Specifically, truck weight surveillance over a large geographical area may logically require larger site numbers Han indicated In He table. For example, many cells in He table indicate the necessity of only 2 or 3 study sites, given certain highway classification and truck ratio conditions.
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sampling efforts to evaluate truck weight enforcement programs. Importantly, designated data collection periods need to be sensitive to seasonal conditions, e.g., agncultural commodity hauling patterns.
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Rural Primary Arterial < 9 % Trucks 9to 30 % Trucks > 30% Trucks Rural Minor Arterial Urban Interstate < 9% Trucks > 9% Trucks Urban Primary Arterial < 9% Trucks > 9% Trucks TOTAL 4 8 4 7 7 14 15 8 8 11 100 18
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Reco~runended WIM Data Collection Site Distribution for ~> ~_~-~ ·< ~ Rural Interstate < 15 % Trucks 15 to 30 °/0 Trucks > 30°/0 Trucks Rural Primary Arteriai < 9 °/0 Trucks 9 to 30 °/0 Trucks > 30°/0 Trucks Rural Minor Arterial Urban Interstate < 9°/n Trucks 2 2 Urban Primary Arterial < 9°/0 Trucks > 9°/0 Trucks _ TOTAL 19 4 (50%)
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Precise site number requirements are determined via application of the data analysis software developed in this project, the Truck Weight Enforcement Evaluation Too!
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percentage of violndon reduction. , Sampling Guide Options LBVBI of s~gan~nce: ~ 0.05 ,~ Clinnnt number of sites: t36 Power of Test: | 0.80 ~ , _ Number of Required Data Collection Sites MOE Percentage of Gross Weight Violators Percentage of Single A,do WL Violators Percentage of Tendem Aide Wt Violators Percentage of Bridge Formula Violetors Average Pounds Over Gross Weight Limit A~rQgs Pounds Over Single Weight Limit Average Pounds Over Tandem Weight Limit Average Pounds Over Bridge Weight Limit Average ESALs Average Excess ESALs Percent change to be detected 5 10 15 20 7 8 6 6 14 12 15 11 18 32 is is 11 10 9 8 10 19 2 3 2 2 9 8 6 11 2 1 2 2 6 5 5 3 3 9 Figure 2.
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Recommended Minimum Site Numbers for Selected M.O.E.s in Corridor-specific Truck Weight Enforcement Evaluations ~SS WIG -- ~ 2 WOLATION:S...-'..',','.',';7.'...~:~: ~''~ EM-.A~E~:: - VIOI'I~iNS;15 to 30 °/0 Trucks 6 > 30°/0 Trucks Rural Primary Arterial < 9 % Trucks 9 to 30 °/O Trucks ~ 30°/0 Trucks Rural Minor Arterial Urban Interstate < 9°/0 Trucks > 9°/0 Trucks Urban Primary Arterial < 9°/0 Trucks > 9% Trucks 1 1 2 3 2 3 i:.
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sampling to evaluate a specific enforcement activity can Involve data collection at a single observation site. The site would be designated as a feasible permanent or portable WIM installation at a highway location affected by trucks subjected to the enforcement procedures under study.
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values between two observed enforcement conditions. It also allows users to conduct an automated pavement design life analysis, estimating the theoretical pavement-life effect res~ting from differences In the two observed enforcement activ~ties.
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Once the program has performed the calculations, the output can be viewed again by pressing the View Results button on the main window. 4.2.1 Starting the Analysis To start a truck weight enforcement analysis, the user activates the program from the program's Main Windlow (Figure 3)
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Modification of these defaults may be necessary depending upon prevailing legal regulations. Enter the legal limits Io' each of the following: Gross Weight Single Axle Weight Tandem Axle Weight {Ibs]
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is designed to assist agencies whose data format does not conform to either the 1995 FHWA Traffic Monitoring Guide 13 Type scheme or Card-7 classification formats. If the user's data are not in either one of these formats, the Convert button is applied to display the TWEET Conversion Utility dialog box which provides an efficient way to convert data files from other formats to the 1995 FHWA Truck Weight Record format.
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Ibe "Enforcement Condition" Dialog Box For each designated enforcement condition, a Number of Files for Condition dialog box asks for the identification of WIM data files Mat pertain to each condition. Up to four files can be utilized for each condition.
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A comprehensive "Help" screen associated with the Pavement Analysis Dialog boxes explains the design theory, including He AASHTO design equations, underlying He computations utilized in the software. As further assistance to He user, Appendix E to this report contains a comprehensive explanation of relevant pavement design considerations and background references regarding overweight axle effects on pavement life.
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TWEET offers Me option of computing this variable based on input values provided by the user. pa Initial Serviceability Index pi Tenninal Serviceability Index MR Default Resilient Modulus ZR Standard Normal Deviate corresponding to design reliability SO Standard Deviation associated wad pavement performance prediction The above parameters are defined arid their design Implications are explained In detailed 'Help' screens in the software.
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According to We specified matenal type, the program wait suggest We most appropriate default Strength Coefficient. Pavement materials and design personnel who curl this software have the option of overriding default values, depending upon their own knowledge of pavement matenals and design procedures along win specific pavement characteristics associated wad We truck weight enforcement location.
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Modulus of Rupture Initial Serviceability Index Terminal Serviceability Index As was the case with the Flexible Pavement Charactenstics box, the most likely default design values have been provided in the case of Rigid Pavements. The user has the option of manually entering values specific to the highway study site.
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The first part of the dialog displays Me observed number of violations, i.e., gross vehicle weight, single axle weight, tandem axle weight, tandem axle weight, and Bridge Formula violations. The second dialog displays the average number of overweight pounds (or Metnc equivalent)
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"Calculated Percentage of Overweight Trucks" Dialog Box The Violation Data by Truck Classification dialog box (Figure 16) indicates violators, by Duck number and percentage, for each class of Duck.
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i,` ~ 1,..e L i;. :,, ~ ~ ; Enforcement Condition Baseline Condition Select truck classification: , i, ,.
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? i Baseline Condition -Average Number of ESALs: Truck Type: Average ESALs: Average Excess ESALs: 2-axle trucks .2468189 0 3-axle trucks .4756302 0 4-axle trucks 2083355 0 5-axle trucks 1.622841 1.573099 6-axle trucks 0 0 7-axle tucks 0 0 All Trucks: 1.?
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HOE Percentage of Gross Weight Yiolators Percentage of Single Axle Weight Yiolators Percentage of Tandem Axle Weight Yiolators Percentage of Tridem Axle Weight Violators Percentage of Bridge Formula Violators Average Pounds over the Gross Weight Limit Average Pounds over the Single Axle Limit Average Pounds over the Tandem Axle Limit Average Pounds over the Trident Axle Limit Average Pounds over the Bridge Formula Limit Average ESALs Average Excess ESALs Sionificant Won-sionificant f Figure I8. "Comparison of Enforcement Conditions" Dialog Box The Sampling Guide dialog box (Figure 19 on page 39)
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Displayed information consists of the calculated pavement ESAL capacity, the estimated pavement life under both observed enforcement conditions, and esti 38
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Violators Percentage of Tandem Axle Wt. Violators Percentage of Bridge Formula Violators Average Pounds Over Gross Weight Limit Average Pounds Over Single Weight Limit Average Pounds Over Tandem Weight Average Pounds Over Bridge Weight Limit Average ESALs Average Excess ESALs Percent change to be detected _ 10 15 20 26 12 26 25 82 77 78 106 369 246 3 6 6 41 38 39 53 185 123 3 3 3 27 26 26 35 123 82 2 1 2 20 19 20 27 92 61 Figure 19.
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