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APPENDIX F M.O.E SAMPLING PLAN DEVELOPMENT INTRODUCTION An essential step in the conduct of NCHRP Project 20-34 was the development of an aid to state highway and enforcement agencies in their determination of how many data-collection sites are required to detect regional M.O.E. differences which may result from a truck weight enforce- ment effort. The applied approach to this process is that the user agency would specify what level of M.O.E. difference (e.g., 5-, ~ 0- , 20-percent) is to be detected. The user would then apply results of this sampling guide, based on a statistical analysis of nation-we M.O.E. data, to determine how many study sites are required. M.O.E sampling requirements were developed on Me basis of M.O.E. distributional data gathered at a sample of LTPP sites. Each site provided 24-hour continuous WIM monitoring and afforded observations of both weekday and weekend traffic. The site utilization strategy for this Sampling Plan development process designated high, intermediate, and low truck volume sites, representative of the following three functional classes: Interstate, Pnmaty Adenal, and Minor Arterial routes. A minimum of Free sites was chosen Mom each of We above functional classification groups. The selection process avoided sites wad very low average ESAL values, as M.O.E.s do need to address violation occurrences. . Table 1 on Me next page lists locations of We sites for which data were collected In the de- velopment of this Sampling Plarl. The selection process designated Me 22 sites noted above, resuming In a highway functional class distribution as follows: 6 Rural Interstates, 6 Rural Pnncipal Arterials, 3 Rural Minor Arteri- als, 4 Urban Interstates, and 3 Urban Primary Arterials . The resulting distribution by region is as follows: ~ Central, 5 West, 4 Atlantic, 5 South. Thus, data were collected for the LTPP sites to fill the functional cIass/truck volume matrix of Table 2 on the next page. Site designations noted in the cells consist of state name abbreviations followed by LTPP site number. ' The substantive contributions to this appendix of Statisticians, Dr. Olga Pendleton of Pen-Hock Statistical Con- sultants, and Ms. Cindy Cornell, of Chaparral Systems Corporation, are gratefully acknowledged. Appenclix F
Table I. Applied LTPP Sites in Sampling Plan Development Arkansas Arkansas Florida Florida Indiana Kansas Kansas Kansas Kentucky Michigan Missouri Missouri Nova Scotia Rhode Island Tennessee Virginia Virginia Washington Washington Washington W:~U~ State Highway I I U 540, Nosh of Sate Highway 253 U.S. 1, South of State Route 442 U.S. 92, East of U.S. 17 State Route 37, Norm of State Route 469 State Route 68 U.S. 50 U.S.166 I-65,Nodh of Lebanon Junction U.S.23, Dundee I - 44, West of Route H I - 435, South of Route 291 Route 201, Kelly Lake I State Route 146, Massachusetts State Line I -75, North of State Route 61 Route 8, Floyd County I - 95, Sussex County State Route 5, South of State Route 104 State Route 14, East of State Route 105 State Route 167, South of State Route 405 State Route 82, West of State Route 22 . . . . . . .. . .. Table 2. Sites selected for sampling plan development % Buck volume Functional Class ~ r Low ~Medium j Rural Interstates T WA7409 ~VAl023 NS6802 TN1023 RuralPrincipalArte- T FL4109 ~RI7401 nals FL4138 KSI006 . Rural Minor Arterials T VA1002 ~ IN2009 None KS1005 . Urban Interstates WA3812 MO4036 AR3059 _ WA3019 . UrbanPrimaryArte- ~WA3813 ~KS4067 rials ~WA6049 l 2 Appendix F High KY3016 MO1010 MI9030 AR3011 None None - None
Sites were not available for some cells, probably due to the fact that such sites are not plentiful in reality. For example, rural minor arterials tend to have low truck volumes and urban highways do not typically support high truck volume as these are not the roads of choice for truckers. At least two sites were needed per cell to provide an estimate of within cell variability needed for developing sample size. In the case of urban interstates with low truck volumes arid urban primary arterials with medium truck volume, only one site was available for those cells so cell sample size could not be developed. However, these sites were used in combining urban in- terstates and primary arterials. Documented truck weight sampling literatures has applied criteria for establishing low, medium, and high truck presence on the traffic stream. Low truck volume sites were considered to contain less than ~ percent Mucks as a proportion of the total traffic volume. Medium truck presence was considered to be in Me range of 8-16 percent trucks, and high truck presence was taken to be greater than 16 percent. Given the documented significance of considering low-, me- dium, and high truck presence, candidate M.O.E. distribution site were accordingly stratified. The noted truck proportion criterion was applied as a guideline; however, due to site availability and observed nationwide traff~c-mix trends (i.e., low rural volumes, producing large truck pro- portions) the applied percent varied slightly from the Texas study. Table 3 presents the truck vol- ume percentages for utilized sites in the Sampling Plan development. Table 3. Percent truck volume for sampling plan development % buck volume Functional Class Low ~Medium Rural Interstates ~7.9, 10.5 ~21.8, 30.2 RuralPrincipalArterials | 3.1,3.6 | 11.4,9.1 . RuralMinorArterials ~4.9,6.8, 10.4 ~None Urban Interstates 4.0 ~ 5.3, ~ 3, 28.3 Urban Primary Arterials ~7.3,8.9 ~23.9 High 61.4, 42.5 41.3, 38.5 None None None 2 Maxwell, D. A. et al, Evaluation of the Texas Truck Weighing Program, Research Report 424-1 F. Texas Trans- portation Institute, College Station, 1X, 1986 3 Appendix F
The Sampling Plan development process first applied a detailed examination of site mlm- ber requirements on the basis of two M.O.E.s, ESALs and Excess ESALs. Statistical distr~bu- tions for these two M.O.E.s were examined for Vehicle Classifications shown in Table 4 below. Given the results of this analysis, a more limited approach was applied with regard to site num- ber requirements on the basis of remaining M.O.E.s. Table 4. Description of Vehicle Classifications vCs vc6 vc7 vc8 vcs vc 10 VC 11 vc 12 vc 13 Two-axle Single Unit Three-axle Single Unit Four or More Axle Single Unit Four or Less Axle Single Trailer Five-axle Single Trailer Six or More Axle Single Trailer Five or Less Axle Multi-Trailer Six-Axle Multi-Trailer Seven to More Axle Multi-Trailer SITE NUMBER REQUIREMENTS FOR ESALs AND EXCESS ESALs Sample size estimates are determined herein for a wide range of precision levels for two M.O.E.'s - percent Excess ESALs and average ESALs. The main purpose in providing estimates over a range of precisions is to give the user some idea of the maximum and minimum sample size requirements Mat exist based on these data. The final sample size determination wall depend on Me factors which are most important In evaluating enforcement and the feasible arid practical expectations for unplementation. Some states may have more resources and want to aim at higher precision levels Man others. Also, the amount of roadway mileage for a particular func- tional class may be greater in some states than others so they may opt to focus on maximizing the precision for that functional class. For example, if a state like Texas believes that enforcement is a bigger problem on rural interstates and there are a tot of miles of rural interstates in Texas, the state may opt to aim for selecting a 20 percent reduction In Excess ESALs after enforcement as opposed to 30 percent, i.e. they want to be able detect a smaller change in violations for this functional class. The precision levels in the sample size computations were based on Minnesota data where truck weights were measured when weight scales were and were not opened. The change in percent Excess ESALs when stations were and were not opened ranged from 2 percent to 30 percent. Hence, the selected range for Excess ESALs in the sampling plan was from 5 to 20 per- cent. The average ESAL`s in these data had relative changes of between 10 to 55 percent of the average when scales were opened to when they were closed 4 Appendix F
Truck weight enforcement effects comparing baseline and enforcement conditions in Idaho were also examined in the development of the Sampling Plan. The Idaho results confirmed application of the 5 to 20 percent range for Excess ESALs and 10 to 50 percent for average ESALs. Sample size tables for each cell of Table 2, i.e., functional class for low-, medium-, and high- truck percentage, are indicated in the discussion which follows. A brief explanation of the interpretation of these tables follow the first cell analysis. Graphs of these changes are also pro- vided. Rural Interstates with Low % Truck Volumes (WA7409,NS6X02) All sample sizes are based on the five- percent significance level with 80% power of detecting the corresponding precisions. Table 5 lists summary statistics, table 6 lists sample sizes for the M.O.E. percent Excess ESALs and table 7 lists these for the M.O.E. average ESALs. Table 5. Sublunary Statistics for Rural Interstates with Low % Truck Traffic 1 WA7409 1 NS6802. ; Vehicle ~ TotalVe- ~ % Excess | Average | TotalVe- | % Excess L Class | hicles | ESA~s | ESA~s | hicles | ESA~s ~. _ 5 46618 0.356 0.1762 64830 2.314 L 6 1 14243 1 0.828 1 0.39411 274581 20.355 _ 7 1862 O 0.9517 144 21.528 ~8 1 20413 1 0.652 1 0.6872 1 42410 1 0.424 L 9 1 150197 1 1.399 1 1.1763 1 109908 1 8.060 L 10 1 8429 1 0.5461 1.1641 242721 27.076 [ r7712 1 2.0361 1.3321 263441 6.111 12 1 8139 0.7621 1.1781 5813 1 26.922 13 ~ 25400 0.169 1 1.7485 5431 1 1.639 1 _ All 1 283013 1.376 1 0.9908 306610 1 8.478 0.9538 1 Average ESALs 0.1464 0.9085 1.4411 0.1051 1.1277 3.2464 0.966 3.732 0 8917 s Appendix F
Table 6. Number of Sites Required to Detect 5-20 percent change in % Excess ESALs. : Percent Charge to be detected Vehicle Class | 5 l 10 | 15 20 l 31 8 1 3 . 6 248 62 28 7 1 32 8 1 4 . 8 10 3 1 9 85 21 9 10 337 84 38 11 1 103 26 1 12 12 217 54 24 13 1 9 2 1 1 1 [ Total ~ 98 1 24 1 11 1 6 2 16 2 s 21 7 14 6 Appendix F
Table 7. Number of Sites Required to Detect ~ 0-50 percent Charge in Average ESALs. Percent Change to be detected Vehicle ~ O 20 30 Class 33 16 11 3 8 113 57 38 10 47 23 16 11 1 5 3 1 2 12 57 28 19 13 22 11 7 All 68 34 23 40 50 8 2 1 28 23 1 12 9 1 14 11 6 17 4 14 Table 6 is to be interpreted as follows: If we want to be able to say Mat a 10 percent de- crease in the percentage of trucks with Excess ESALs after enforcement is a statistically signifi- cant reduction in violations (at the 5 % level with 80% power), and if we are most interested in detecting this for vehicle class 9, we will need 21 sites. If we are willing to lower our precision requirement to detecting a 20 percent reduction in Excess ESALs, we can do this with only 5 sites. If we want to do this for all vehicle classes, we will need 6 sites. Table 7 focuses on the M.O.E. of average ESALs. For vehicle class 7 to declare a 30 percent reduction in average ESALs as a statistically significant reduction due to enforcement, three sites are needed. To detect this for vehicle class 8, 38 sites are needed. Thus, it is impor Appendix F
tarot to know which vehicle class is most important and this may well be determined by the per- centage of vehicles in this class typically travel rural interstates or by the class with the highest percentage frequency of Excess ESALs. Figure 1 provides the total vehicle frequency distribu- tion arid figure 2 the frequency distribution of vehicles with Excess ESALs (violators) by vehicle class. Figures 3 arid 4 show sample size requirements for each vehicle class (corresponding to tables 6 and 71. Since vehicle class 9 was dominant in both frequency on rural interstates with low truck volume arid frequency of violations (percent Excess ESALs), we might focus on this vehicle class In determining sample size. In this case, 5 sites would be sufficient to detect a 20 percent change in Excess ESALs and a 10 percent change in average ESALs on rural interstates with- truck volumes of 7-10 percent. Rural Interstates with Medium % Truck Volumes (VAl023,TNI023) Table 8 lists summary statistics, table 9 lists sample sizes for the M.O.E. percent Excess ESALs and Table 10 lists these for the M.O.E. average ESALs. Table 8. Summary Statistics for Rural Tnterstates with Medium % Truck Traffic . l ~ VAl 023 ~ TN1023 Vehicle ~ TotalVe- ~ %Excess ~ Average ~ TotalVe- ~ %Excess | Class ~ hicles ~ ESALs ~ ESALs ~ hicles ~ ESALs 5 ~1 2802 ~2.114 ~01188 ~113763 ~1 .908, 6 1 15928 5.198 1 0.413713879 1 14.338 . 7 1 413 1 26 877 1 2 2417 1920 1 57.609 _ _ _ 8 1 91545 1 1.784 1 0.2861 137618 1 13.563 9 1 785951 1 9.86i 1 1.4935 1448886 1 27.038 10 1 4951 3.016 1 0.9927 13417 1 20.076 11 1 43397 1 10.174 1 1.7424 130237 1 39.257 12 1 3786 1 0.924 1 0.7539 15295 1 7.970 13 1 349 1 6.304 1 1.4010 13525 1 38.922 1 1 All 1 1109112 1 7947 1 1.1818 1657540 1 24.206 1 2.4250 Average ESALs 0.9241 1.1493 5.7411 1.2974 2.8013 2.8910 4.2635 2.0508 6.1977 8 Appendix F
Table 9. Number of Sites Required to Detect 5-20 percent charge In % Excess ESALs. Percent Change to be detected Vehicle Class ~5 10 ~15 20 5 1 136 34 1 15 6 1 180 45 1 20 7 1 524 131 1 58 8 1 104 26 1 11 9 1 284 71 1 32 10 1 188 47 1 21 11 1 362 90 1 JO 12 1 100 25 1 11 13 1 484 121 1 54 1 Total 1 252 1 63 1 28 1 16 11 33 6 18 12 23 6 3() 9 Appendix F
Table 10. Number of Sites Required to Detect 10-50 percent Charge in Average ESALs. | Percent Change to be detected Vehicle I 10 20 1 30 1 40 5 1 125 1 63 1 42 1 31 6 1 70 1 35 1 23 1 18 7 1 65 1 33 1 22 1 16 8 1 95 1 47 1 32 1 2 9 1 45 23 1 15 1 11 L 10 1 73 T 36 1 24 : 18 1 1 11 1 62 1 31 1 21 1 16 1 l 12 68 34 23 17 . L 13 1 94 1 47 1 31 1 23 1 ~ [ All 1 45 1 30 1 23 | 18 50 25 14 13 19 9 15 12 14 19 Since vehicle class 9 was dominant in bow frequency on rural ~nterstates with medium truck volume and frequency of violations (percent Excess ESALs), we again focus on this vehi- cle class in determining sample size. In this case, 18 sites are needed to detect a 20 percent change in Excess ESALs and a 20-30 percent change in average ESALs have to occur to con- clude Mat enforcement was successful on rural interstates with truck volumes of 20-30 percent. 10 Appendix F
Rural Interstates with High % Truck Volumes (KY3016,MOlOlO) Table 11 lists sublunary statistics, table 12 lists sample sizes for the M.O.E. percent Excess ESALs and Table 13 lists these for the M.O.E. average ESALs. Table 11. Summary Statistics for Rural Interstates w~th Low % Truck Traffic | KY3016 r MO1010 . . . Vehicle | To~Ve- | %Excess | Average | TotalVe- T %Excess ~ Class | hicles | ESALs | ESALs | hicles | ESALs | 5 1111747 1 3.929 1 0.2442 1291531 1 0.763 6 1330411 15.2421 1.4038115282 T 27.164 7 125471 61.7981 S.99051904 T 43.142 ~ 8 1790921 7.3931 0.7362174754 T 3.203 9 19698681 18.2391 1.8413147l43sT 12.5901 10 139221 14.3291 S.345712207 T S.437 11 155438 ~18.7671 2.6332740224 14.974 12 17145 3.639 1 2.48965442 1 5.7332 13 11888 ~14.6721 36.61192T 0OOO ~. . ~ All 1 1264688 1 16.229 1 1.7292 1 935672 1 8.557 1 Average ESALs ~1 1 0.0479 2.151 4.380 0.368 2.109 1.232 - 1 2.592 1.178 0.2427 11 Appendix F
Table 12. Number of Sites Required to Detect 5-20 percent change in % Excess ESALs. | Percent Change to be Detected Vehicle Class | 5 | 10 | 15 | 20 5 1 34 8 1 4 6 1 324 81 1 36 7 1 516 129 1 57 8 1 107 26 1 12 9 1 288 72 1 32 10 1 208 52 1 23 11 1 291 73 1 32 12 1 91 23 1 10 13 1 253 63 1 28 Total 1 273 59 1 26 15 2 20 32 7 18 13 18 6 16 12 Appendix F
Table ~ 3. Number of Sites Required to Detect ~ 0-50 percent Change in Average ESALs. - I . Percent Change to be detected Vehicle I 10 1 20 1 30 1 40 1 50 ; 5 95 47 32 24 19 .. . 8 23 12 8 6 5 9 1 1 I ~1 1 1 1 10 82 41 27 21 16 12 27 13 9 7 5 13 1 205 102 1 68 51 1 41 ~- [ All 1 460 T 230 1 153 T 115 1 92 1 Since vehicle class 9 was dominant in both frequency on rural interstates with high buck volume and frequency of violations (percent Excess ESALs), we again focus on this vehicle class in determining sample size. In this case, 7 sites are needed to detect a 20 percent change in Ex- cess ESALs and this wait be sufficient to detect as little as a 10 percent change in mean ESALs on rural ~nterstates with truck volumes of 40-60 percent. 3 Appendix F
Rural Primary Arter~als with Low TO Truck Volumes (FL 413S, FL 4138) Table 14 lists summary statistics, table 151ists sample sizes for the M.O.E. percent Excess ESALs arid Table 16 lists these for the M.O.E. average ESALs. Table 14. Summary Statistics for Rural Pr~mar~v Arterials with Low % Truck Traffic ~I FL 4109 1 | Vehicle | Total Ve- | % Excess ~ Average | TotalVe Class hiclesESALsESALshicles ; 5 ~9914 ~0.1111 ~0.0073 ~4492 6 ~181 ~36.464~4.531 ~437 7 ~72g.571 ~7.224 ~4 30112.957~1.5670~303 9 ~25710.506~1.523 ~152 10 ~1o.ooo ~O.958 ~8 11 ~14 ~1.8300 ~3 1 1 12 ~30.0000 ~0 13 ~0 ~I I All ~10678 ~1.376 ~.0172 ~5400 ~5.574 ~0.5524 FL 4138 % Excess ESALs Average ESALs 1.135 0.0540 33.638 3.471 100.00 13.524 23.762 2.930 15.789 1.700 25.000 2.2400 n non () 152 14 Appendix F
Table 15. Number of Sites Required to Detect 5-20 percent change in % Excess ESALs. . | Percent Change to be detected 1' Vehicle Class 5 10 15 ~20 5 1 9 1 2 T 1 r ~ 6 475 118 53 7 1 521 130 T 58 8 1 315 79 T 35 230 57 T 26 0 1 363 91 T 40 1 1 218 55 T 24 ~ 11 1 57 1 14 T 6 T 4 1 30 33 20 14 23 14 15 Appendix F
Table 16. Number of Sites Required to Detect 10-50 percent Change in Average ESALs. Percent Change to be detected I Vehicle 1 10 T 20 1 30 1 40 1 50 1 Class I l l I 5 122 61 41 30 6 4 2 1 1 7 19 10 6 5 . 8 19 10 6 5 10 34 17 1 1 8 1 1 96 48 32 24 All 1 151 1 76 1 50 1 38 24 4 4 1 7 19 Vehicle class 5 was dominant in total Dequency on rural primary arterials with low truck volume and vehicle class 6 was Me class with the highest frequency of violations (percent Excess ESALs). There is a wide variability in the sample size requirements for these two vehicle classes for the two M.O.E.'s. However, it would appear that a sample size of 30 sites are needed to de- tect a 20 percent change in Excess ESALs and a 40 percent change in average ESALs have to occur to conclude that enforcement was successful on rural primary arterials with truck volumes of 3 to 4 percent. This probably suggests that it is not practically feasible to attempt to evaluate M.O.E.'s on primary rural arterials at these low truck volumes. 16 Appendix F
Rural Principal Arierials with Medium % Truck Volumes Table 17 lists summary statistics, table 18 lists sample sizes for the M.O.E. percent Excess ESALs and Table 19 lists these for the M.O.E. average ESALs. Table 17. Summary Statistics for Principal Arter~als with Medium % Truck Traffic 1 RI7401 1 KS 1006 Vehicle Total Ve- % Excess AverageTotal Ve-% Excess Class hicles ESALs ESALshiclesESALs 5 ~86928 7.228 ~0.3886450 ~3.008 18605 23.101 ~3.571822 ~3.041 ~1058 84.405 ~20.20314 ~14.286 8 ~60449 14.394 ~1.4601160 ~0.603 ~173950 26.668 ~6.2263666 ~4.255 10 ~1934 32.989 ~5.83540 ~2.500 11 ~981 15.494 ~2.18767 ~1.493 2 ~49 32.653 ~4.91529 ~0 13 ~22 50.000 ~10.63122 ~0 . , All ~343976 21.106 ~3.800 ~12270 ~3.146 0.396 Average ESALs 0.164 . 0.465 1.547 0.229 0.827 0.968 0.486 0.204 0.849 7 Appendix F
Table 18. Number of Sites Required to Detect 5-20 percent change in % Excess ESALs Percent Charlge to be detected 1 Vehicle Class | 5 | 10 | 15 1 20 5 1 136 1 34 1 15 1 8 6 364 91 40 290 73 32 255 64 28 _ 434 109 48 . 10 460 115 51 11 1 264 1 66 1 29 12 343 86 38 . . 13 1 394 1 99 1 44 , All 1 342 1 86 1 38 1 21 23 18 16 27 29 17 21 25 18 Appendix F l
Table ~ 9. Number of Sites Required to Detect 10-50 percent Charge in Average ESALs 1 Percent Change to be detected= Vehicle ~10 T 20 T 30 ~40 Class ~ 5 ~35 17 ~12 ~9 6 125 63 42 31 7 1 155 77 1 52 1 39 8 1 112 56 1 37 1 28 1 9 1 123 62 1 41 1 31 T 10 1 108 1 54 1 36 1 27 - 11 85 43 28 21 , 12 178 89 59 45 13 153 76 51 38 All 1 233 1 117 1 78 1 58 1 47 50 7 25 31 22 25 22 17 36 31 Sample size requirements are high for this category because of the large differences in % Excess ESALs and average ESALs between these two sites. For example, for vehicle class 7 (see table 17) R] 7401 had 84% Excess ESALs whereas KS 1006 had only 14%. For this saline vehicle class, average ESALs were 20.2 for R] and 1.5 for KS. Similarly, for vehicle class 13 R! had 50% Excess ESALs arid KS had none. These data should be reexamined to determine if these discrepancies are indeed correct. Perhaps some vehicle classes should be omitted if they are providing less reliable data. Since vehicle class 9 was dominant in both total frequency on rural primary arterials with medium truck volume and frequency of violations (percent Excess ESALs), we again focus on this vehicle class in determining sample size. In this case, 27 sites would be required to detect a 20 percent change in Excess ESALs and a 50 percent change would be required to declare a sig- nificant reduction in average ESALs due to enforcement for rural primary arterials with 9-11 % Muck volume. . 19 Appendix F
Rural Principal Arterials with high Restruck Volumes (AR3011, MI9030) Table 20 lists summary statistics, table 21 lists sample sizes for the M.O.E. percent Excess ESALs and Table 21 lists these for the M.O.E. average ESALs. Table 20. Summary Statistics for Rural Principal Arterials with High % Truck Traffic 12433 7.36 my: Vehicle Total Ve- % Excess Average Class hicles ESALs ESALs 5 1408 1.207 0.1667 T460 5.2171 0.4463 . 7 45 44.44 2.6913 T1428 5.742 1 0.6385 9 112287 6.885 1 1.249 . 10 154 12.338 2.336 l 11 1159 1.898 1.082 12 84 11.905 1.885 13 16 o.ooo 1 0.360 11 All 117031 6.107 1 1.092464657 1 6.597 1.142 MI9030 1 1 1 Total Ve- hicles 50278 % Excess ESALs Average ESAI,s . 1 1 . 1 1 6.317 0.8971 0.5745 T 693 13.997 1.356 22178 2.511 0.5247 . 1 331716 7.089 1.1588 14133 6.439 1.7154 16821 2.931 1.480 6193 6.346 1.946 1()212 5 631 2.121 20 Appendix F
Table 21. Number of Sites Required to Detect 5-20 percent change in % Excess ESALs. l | Percent Change to be detected l | Vehicle Class | 5 | 10 | 15 ~I 5 122 30 14 . . 6 1 146 1 36 1 16 280 1 70 1 31 81 55 1 14 1 6 138 1 35 1 15 101 128 32 1 14 . 11 58 15 7 12 126 32 14 13 ~112 28 ~12 : ~Tom ~129 ~32 ~14 ~8 20 8 9 18 4 9 8 4 8 7 21 Appendix F
1 Table 22. Number of Sites Required to Detect 10-50 percent Change in Average ESALs. Percent Charge to be detected Vehicle 1 0 20 30 40 5 1 99 50 1 33 25 3 2 1 1 1 23 11 1 8 6 1 2 1 1 1 1 10 1 5 2 ~2 1 12 1 1 1 1 13 105 53 35 26 All 36 18 12 9 7 50 20 s 1 1 21 Since vehicle class 9 was dominant in both total frequency on rural primary arterials with high truck volume and frequency of violations (percent Excess ESAL`s), we again focus on this vehicle class in determining sample size. In this case, 9 sites would be sufficient to detect a 20 percent change in Excess ESALs and a 10 percent change in average ESALs would be declared a statistically significant reduction due to enforcement for rural primary arterials with about 40 percent truck volumes. 22 Appendix F
Rural M~nor Arter~als with Low °/O Truck Volumes Table 23 lists su~nary statistics, table 24 lists sample sizes for the M.O.E. percent Excess ESALs and Table 25 lists these for the M.O.E. average ESALs. Table 22. Summar~v Statistics for Rural Minor Arterials w~th Low % Truck Traff~c 1 KS 1005 1 IN2009 1 VA 1002 VC | Tot3] | %Ex- | Avera'~e | Tota} | °,,Ex-| Average | Tol~ | %Ex- cess | ESAL s I | ~ ,ess I ESALs | I cess 5 17l~l9 1 4.87 1 0.2 4 1 56009 1 3.86 1 0.184 1 15488 1 17.46 6 1 76 1 l7.4 T 0agl4T ,45281 6071 05881 8'47T 28171 7 113 1 23.1 T 2.2'4 1 3455 1 70.2 1 4.381 T ,< 16 T 75 93 8 T~'5 1 1.96 T 0.3'41 99621 3.981 0.563: 5483T 1573 [9 1 138li 1 5.84 T 08631 472451 ;051 1027T 82~7T 14901 67 1 2.98 T 0.8671 84,1 4.41 0.963 T ,.21 16.07 ,l 1 (~4 1 1.56 T 0.1'61 950120.21 2.226 T "4T 16.18 12 1 ~ 1 0 T 0.11iT 4SI F.441 1.329: 6T o1 13 1 1 0 T 1~06)l 2sl ol 2.056 t 3T ol ~ --1 All 1 10653 1 5.58 1 0.373 1 133060 1 1i.37 1 0.705 1 395~6 1 21.23 1 1.885 Avg ESAL 1.250 2.290 6.844 1.646 1.840 1.921 2.694 1.209 0.160 23 Appendix F
rig Vehicle Class 87 I 10 ~15 ~20 22 10 s 6 169 42 19 11 18 7 283 71 31 8 100 25 11 6 9 85 21 9 8 s 64 10 11 12 74 18 s 16 4 51 13 6 3 13 o o o o All 1 121 1 30 1 13 1 8 24 Appendix F
Table 25. Number of Sites Required to Detect 10-50 percent Change in Average ESALs. . I Percent Change to be detected Vehicle I 10 20 | 30 40 | Class l l l l 128 1 64 1 43 1 32 6 1 53 1 27 1 18 T 13 28 1 14 1 9 T 7 8 1 67 1 33 1 22 1 17 9 1 19 1 9 1 6 T 5 1 4 10 1 23 1 11 1 8 T 6 11 1 65 1 33 1 22 1 16 12 1 60 1 30 1 20 1 15 13 1 85 T 42 1 28 T 21 All 1 100 1 50 1 33 1 25 50 26 11 6 13 5 13 12 17 Sample size requirements are high for vehicle class 7 on percent Excess ESALs primarily due to rN 2009 Mat had 70% of We vehicle in this class as overweight. These data again should be checked for realistic accuracy and perhaps some vehicle classes should be omitted if they are providing less reliable data. Vehicle class 5 was Me most dominant in tote] frequency for rural minor arter~als with low truck volumes. At least 26 sites would be required to declare even a 50 percent reduction in average ESALs as statistically significant. For the M.O.E. Excess ESALs, 5 sites would be suf- ficient to declare a 20 percent reduction as significant for rural minor arterials with 5-10 percent truck volumes. 25 Appendix F
Urban Roadways The LTPP database only had the minimum number of sites needed to develop sample size (two or more) for urban interstates with medium truck volumes (13-28 % trucks) and urban primary arterials with low percent truck volume (7-9 % trucks). Thus, in addition to developing sampling requirements for these two cells, all urban roads (interstate and primary arterials) were combined to provide sampling requirements for low and medium percent truck volume (see table 11. There were no sites available for urban high truck volumes for either interstates or primary arterials probably because these roads do not, in practice, experience high truck volumes. Urban Interstates with Medium % Truck Volumes (MO 4036, AR 3059, and WA 3019) Table 26 lists summary statistics, table 27 lists sample sizes for the M.O.E. percent Excess ESALs and Table 27 lists these for the M.O.E. average ESALs. Table 26. Summary Statistics for Urban Interstates with Medium % Truck Traffic MO 4036 AR 3059 WA 3019 VC Total o/o Ex- Average Total onto Ex- AverageTotal o/o Ex cess ESALs cess ESALs cess 5 11428 18.329 1 0.54 1 6506~181 0.19191 150941 2.111 6 112~38 126.30 1 2.85C 1 1741112 36 l 0.8221 42071 2.139 7 197 1 84.39 1 13.4 1 253 1 61 56 1 4.503 1 3~52 1 42.76 8 122(88 1 5.781 1 0.680 1 1960 1 2'.E 57 1 0 344 1 5647 1 1 045 211542 113.24 1 1.708 1 6261114 98 l 2.4641 1361181 6.407 10 1750 16.17 3.026 165 9.091 2.338 16202 1.531 11 27809 12.17 1.901 121 0.826 0.455 9579 4.186 12 3437 10.30 2.055 23 0 0.663 8099 1.358 13 900 7.778 2.204 9 0 0.574 13883 1.116 _ L All 1 295889 1 13 06 1 1 656 1 133060 ~ 9 308 1 1 196 1 212791 1 5 487 1 1 091 Avg ESAL 0.164 0.275 2.233 0.333 1.259 0.795 1.012 0.824 1 281 26 Appendix F
Table 27. Number of Sites Required to Detect 5-20 percent change in % Excess ESALs. . l Percent Change to be Detected , T Vehicle Class ~5 ~10 ~15 ~20 5 64 16 7 6 1 218 55 1 24 7 350 88 39 8 1 63 16 1 7 9 133 33 15 10 1 41 10 1 5 1 1 1 127 32 1 14 12 1 56 14 1 6 13 1 21 5 1 2 1 All 124 31 - 14 8 4 14 22 4 8 3 8 4 27 Appendix F
Table 28. Number of Sites Required to Detect 10-50 percent Change in Average ESALs. ,. Percent Charge to be Detected . Vehicle ~10 ~20 ~30 ~40 Class 74 ~37 ~25 ~19 6 108 54 36 27 7 93 46 31 23 8 46 23 15 11 9 35 18 12 9 10 59 29 20 15 11 68 34 23 17 12 1 68 1 34 1 23 1 17 13 1 63 1 32 1 21 1 16 All 1 149 74 1 50 1 37 1 30 50 15 22 , 19 9 7 12 l 14 14 13 Sample size requirements are high for vehicle classes 6 arid 7 on percent Excess ESALs primarily due to MO 4036 which had 26% and 84% of the vehicles in this class as overweight when the other sites had far less. These data again should be checked for realistic accuracy and perhaps some vehicle classes should be omitted if they are providing less reliable data. Since vehicle class 9 was dominant in both total frequency arid frequency of violations (percent Excess ESALs) on urban interstates with medium truck volume, this will be our focal point in sample size determination. In this case, 15 sites would allow a declaration of a 15 % re- duction in Excess ESALs and a 30 percent reduction in average ESALs to be a statistically sig- nificant indicator of an effective enforcement program for urban interstates with 13-28 percent truck volume. 28 Appendix F
Urban Interstates and Primary Arierials with Medium % Truck Volumes (MO4036, AR3059, WA3019, and KS4067) Table 29 lists summary statistics for urban primary arterials (KS 4067 - urban interstate summary statistics were listed in table 26), table 301ists sample sizes for the M.O.E. percent Ex- cess ESALs and table 31 lists these for the M;O.E. average ESALs. Table 29. Summary Statistics for Primary Arterial with Medium % Truck Traffic (KS40671. KS4067 Vehicle Class Total % Excess 5 20152 2.233 6 5730 11.187 7 112 12.5 8 7483 6.027 9 109456 6.837 10 1963 2.598 11 11551 4.969 12 1 746 1.877 13 1661 1.505 Total 1 158854 6.108 Average ESALs 0.184 0.795 1.732 0.565 1.322 1.188 1.439 0.660 1.332 1.127 29 Appendix F
Table 30. Number of Sites Required to Detect 5-20 percent change in % Excess ESALs. I Percent Change to be Detected Vehicle Class | 5 | 10 | 15 | 20 . 5 53 13 6 3 6 201 50 22 350 1 88 1 39 8 66 17 7 9 123 31 14 10 40 10 5 11 114 28 13 12 52 13 6 13 21 5 2 [ All ~115 1 29 1 13 ! 7 13 22 4 8 3 7 3 1 30 Appendix F
Table 30. Number of Sites Required to Detect 10-50 percent Charge in Average ESALs. , l Percent Change to be Detected Vehicle 10 20 30 Class ~. 5 48 24 16 6 97 48 32 104 52 35 8 13 7 4 . 9 11 6 4 . 10 33 16 11 . 11 28 14 9 . 12 43 22 14 . All 1 204 102 1 68 51 1 41 40 12 50 10 24 19 26 21 3 3 3 2 8 7 7 6 11 9 6 Since vehicle class 9 was dominant in bow total frequency on urban interstates and he- quency of violations (percent Excess ESALs), this will be our focal point in sample size deterrni- nation. In this case, 15 sites would allow a declaration of a 15 % reduction in Excess ESALs and a 10 percent reduction in average ESALs to be a statistically significant indicator of an effective enforcement program for urban interstate s and primary arterials with 13-28 percent truck volume. 31 Appendix F
Urban Primary Arter~als with Low % Truck Volumes (WA 3813, WA 6049) Table 32 lists summary statistics, table 33 lists sample sizes for the M.O.E. percent Excess ESALs and Table 341ists these for the M.O.E. average ESALs. Table 32. Summary Statistics for Urban Primary Arterials with Low % Truck Traffic 1 WA3813 1 WA6049 Vehicle ~ To~Ve- | %Excess ~ Average | TotalVe- ~ %Excess Class hicles ESALs ESALs |hicles | ESALs . 5 141473 1 3.947 1 0.28901420144 1 2.927 6 123898 1 7.5911 1 0.6638 1151406 1 3.453 7 1311 1 10.006 1 1.6908 16833 1 6.586 8 112707 1 2.849 1 0.3850168363 1 2.233 9 46167 11.287 1.4753492414 1 3.827 10 17730 4.585 0.876878564 1.148 11 13153 1 12.908 1 1.690444956 1 5.085 12 13980 1 5.276 1 1.310336356 1 2.580 13 116097 5.237 1 1.8900 166500 1 1.290 1 All T1655161 6.8591 0.9540114655361 3.1091 0.51~09 Average ESALs 0.1712 0.3194 0.9614 0.3743 0.6937 0.6166 0.9464 0.7667 1 479n 32 Appendix F
1 Table 33. Number of Sites Required to Detect 5-20 percent charge in % Excess ESALs. | Percent Change to be Detected Vehicle Class | 5 | 10 | 15 l 5 1 62 15 1 7 6 1 81 20 1 9 1 138 35 1 15 8 1 47 12 1 5 1 go 22 1 10 10 1 37 9 1 4 1 1 1 91 23 1 10 12 1 58 13 1 6 13 1 53 13 1 6 All 1 71 1 18 1 8 1 4 20 4 s 9 3 6 3 6 3 3 33 Appendix F
Table 34. Number of Sites Required to Detect 10-50 percent Change in Average ESALs. ~ Percent Change to be Detected . Vehicle 10 20 30 Class - s T 38 1 19 1 13 6 T 52 1 26 1 l7 L 7 T 41 1 21 r 14 8 T 2 1 1 1 1 ~9 T 54 1 27 1 18 10 T 26 1 13 r 9 1 11 T 42 1 21 r 14 T 12 T 40 1 19 1 13 3 T 18 1 9 1 6 All T 62 T 31 r21 40 50 10 8 13 10 10 8 1 1 15 11 6 s 10 8 10 8 s 16 4 12 The most prominent vehicle classes in both total frequency and frequency of violations (percent Excess ESALs) on urban primary arterials troth low truck volume were vehicle class 9 and 5, respectively. Examining the sample size requirements for these classes, 15 sites would allow a declaration of a 15 % reduction in Excess ESALs and a 40 percent reduction in average ESALs to be a statistically significant indicator of an effective enforcement program. If we were only interested in the M.O.E. of Excess ESALs, only 7 sites would be necessary to detect a sig- n~ficant difference for urban primary arterials with 7-9 percent truck volume. 34 Appendix F
Urban Interstates and Primary Arterials with Low % Truck Volumes VIVA 3813, WA 6049, WA3XI2) Table 35 lists sublunary statistics for urban interstates with low truck volume (table 33 lists these for primary arterials), table 35 lists sample sizes for the M.O.E. percent Excess ESALs and Table 37 lists these for the M.O.E. average ESALs. Table 35. Summary Statistics for Urban Interstates (WA 3812) with Low % Truck Traffic WA 3812 C ~Total | %Excess | 5 264994 0.702 6 32771 3.405 7 3157 5.195 8 57515 0.847 9 221963 1.029 10 30794 0.786 11 13081 0.742 12 10535 1.187 13 32901 0.602 All 1 667711 T 0.984 T 0.476 Average ESALs 0.077 0.439 0.804 0.412 0.749 0.848 0.871 0.815 1.366 3s Appendix F
Table 36. Number of Sites Required to Detect 5-20 percent charge in % Excess ESALs. ~Percent Change to be Detected | Vehicle Class 5 10 15 5 30 7 3 6 53 13 6 7 1 85 21 1 9 8 1 27 7 1 3 1 47 12 1 5 10 1 21 1 2 11 1 61 15 1 7 12 1 34 9 1 4 13 1 23 6 1 3 All 1 38 9 1 4 2 20 2 3 1 4 2 1 36 Appendix F
Table 37. Number of Sites Required to Detect 10-50 percent Change in Average ESALs. Percent Change to be Detected , _ 10 20 30 5 37 19 12 6 14 7 5 7 18 9 6 21 11 7 4 2 1 16 8 5 l 10 5 3 All 1 36 1 18 1 12 1 9 1 7 Vehicle Class 40 9 4 4 50 7 4 8 9 5 4 10 1 11 4 1 ~ 3 13 1 1 The most prominent vehicle classes in both total frequency and frequency of violations (percent Excess ESALs) on urban interstates and urban primary arsenals wad low truck volume were vehicle classes 9 and 5, respectively. Examining the sample size requirements for these classes, 9 sites would allow a declaration of a 10-15 % reduction in Excess ESALs and a 40 per- cent reduction in average ESALs to be a statistically significant indicator of an effective en- forcement program. If we were only interested in the M.O.E. of Excess ESALs, only 5 sites would be necessary to detect a significant difference for urban interstates and primary arterials with 4-9 percent truck volume. 37 Appendix F
ESALs and Excess ESALs Sampling Requirements Conclusion Depending on the M.O.E. of interest, the required sample sizes differ. Detecting changes in percent Excess ESALs generally requires more samples than detecting a percentage change in Excess ESALs. That is, if we are most interested in declaring a ~ 5 percent reduction in the per- cent of Vehicle Class 9 trucks with Excess ESALs after enforcement, this requires more sites than if we want to be able to say that the reduction in average ESALs was ~ 5% less than the av- erage ESALs before enforcement. Table 38 shows the number of sites for detecting a 15 percent change in excess ESAL change and table 39 shows the number of sites required to detect a 30 percent change in average ESALs (detecting a ~ 5 percent change in average ESALs is probably an unrealistic). Alternative site number requirements to these can be constructed from preceding tables in this report in order to assess the significance of other observed ESAL changes. Table 38. Number of sites required to detect a ~ 5% charge in Excess ESALs. % truck volume . . Functional Class ~Low Medium Rural Interstates 9 32 Rural Principal Arte- | 2 15 nals RuralMinorArterials | 9 l Urban Interstates 15 Urban Principal Arte- ~10 , nals Barbara Interstates and 10 14 Pnncipal Arterials Combined Tom | 30 ~ 5 High 32 15 47 38 Appendix F
Table 39. Number of sites required to detect a 30°/O change in average ESALs. _. . TO truck volume . Functional Class Low Medium Rural Interstates 2 ~ 5 Rural Principal Arte- 2 4 reals Rural Minor Arteriole 6 Urban Interstate s 12 Urban Principal Arte nals . Urban Interstates and 5 4 Pr~ncipla Arter~als Combined Total 1 5 60 High 2 2 4 SITE NUMBER REQUIREMENTS FOR OVERWEIGHT VIOLATIONS Given the foregoing detailed development of ESAL and Excess ESAL sampling reqliire- ments, a more streamlined approach was applied with regard to the remaining M.O.E.s, i.e., Pro- portion of trucks with Gross Weight Violations' Proportion with Tandem Violations' arid Pro- portion with Single Axle Violations. On the basis of field observations and preliminary Sam- pling Plan developmental effort, it was evident that M.O.E. development needed to concentrate on the Vehicle Class 9 truck type as these were the predominate truck type and He predominate violators. Therefore, development of sampling requirements for these measures addressed M.O.E. distributions exhibited by Type 9 trucks at the 22 LTPP sites. As in the process which established ESAL and Excess ESAL sampling requirements, ac- tual truck weight enforcement effects were examined for existing project databases, e.g., Califor- nia, Georgia, Idaho, and Minnesota. On the basis the data examination, sampling requirements were developed to accommodate the detection of 10-, 20-, 30-, 40- and 50-percent changes in the M.O.E.s. 39 Appendix F
Proportion of Gross Truck Weight Violations Table 40 below indicates the required site numbers to detect changes in the proportion of trucks exceeding the legal gross weight limit, given the specified detection level thresholds. Table 40. Site Number Requirements for Gross Truck Weight Violations 11 PERCENT CHANGE TO BE DETECTED FUNCTIONAL CLASS 10 ~20 l 30 ~50 Rural Interstate < 15 % Trucks 40 10 15 to 30 %; 24 Trucks > 30% Trucks 48 12 Rural Primal Arterial < 9 TO Trucks 40 1 0 9 to 30 % Trucks 105 26 . > 30°/O Trucks 20 5 Rural Minor Arterial 44 1 1 Urban Interstate < 9% Trucks 5 1 > 9% Trucks 25 6 Urban Primary Arterial < 9% Trucks 32 ~ > 9°/O Trucks ~ ~ 49 ~12 2 4 s 2 2 2 4 2 . . 2 s 1 l 3 4 2 The shaded cell above indicates the most likely expected percent change and site re- qu~rements to be associated wad truck weight enforcement activity on Me basis of field observa- tions conducted in the current study. Proportion of Trucks with Overweight Tandem Violations Table 41 on the next page indicates the required site numbers to detect changes in the proportion of trucks exhibiting at least one tandem axle pair that exceeds the legal weight limit, given the specified detection level thresholds. 40 Appendix F G; .... .,
Table 4 1. Site Number Requirements for Tandem Weight Violations PERCENT CHANGE TO BE DETECTED . FUNCTIONAL CLASS 10 20 Rural Interstate < 15 TO Trucks 54 13 15 to 30 % Trucks 24 > 30% Trucks 48 12 Rural Primary Arterial < 9 % Trucks 40 1 0 9 to 30 % Trucks 105 26 > 30% Trucks 20 5 Rural Minor Arterial 44 1 Urban Interstate < 9% Trucks 5 3 > 9°/0 Trucks 25 6 Urban Primary Arterial _ < 9°/0 Trucks 32 ~ > 9°/O Trucks 49 12 _ ~ ~ ~ ~ ~ _ ~ ~ i 1 1 ~ _ ~ ~ ~ _ ~ ~ ~ ~ ~ 1. l ~ ~ ~ i . _ E wee i' ~ _ _ ~ ~ i2~i2ff _' i_ ~ He _3 i jA~_i ~ _i Ray _~ it= _ ___ __ _ ~ _ __ __ _ _ ___ _ _ ___ ~ _ _~ _ ma_ _ _ _ .~ ~ _~ __ ~ _ _ _ _ ~ _ ~3 _ __ 30 50 4 1 s 2 4 2 4 12 2 s 2 4 2 l 1 2 4 s 2 The shaded cell above indicates the most likely expected percent change and site re- qu~rements to be associated with truck weight enforcement activity on the basis of field observa- tions conducted in the current study. Proportion of Trucks with Single Axle Weight Violations: Table 42 on We next page indicates the required site numbers to detect changes in the proportion of trucks exhibiting at least one overweight axle which exceeds We legal weight Innit, given the specified detection level thresholds. 41 Appendix F
Table 42. Site Number Requirements for Single-AxIe Violations PERCENT CHANGE TO BE DETECTED FUNCTIONAL CLASS 10 _| 30 40 Rural nte ate <15%Trucks 1 33 ~4 LO is to 30 % Trucks 84 81_ 5 > 30% Trucks 50 _ 6 - 3 Rural Primary Arterial ~ < 9 % Trucks 45 Em_ 5 3 9 to 30 % Trucks 98 ~ ~6 > 30% Trucks 20 ~j 2 1 Rural Minor Arterial 36 ~4 2 Urban Interstate < 9% Trucks 7 > 9% Trucks 24 ~3 Urban Prima Ar erial < 9% Trucks 1 28 ~3 LO > 9% Trucks 3 ~3 2 5(} 2 3 . 2 2 4 l l l 42 Appendix F
