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Review of Truck Characteristics as Factors in Roadway Design (2003)

Chapter: Appendix B - Weigh Station Data Collection

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Page 127
Suggested Citation:"Appendix B - Weigh Station Data Collection." National Academies of Sciences, Engineering, and Medicine. 2003. Review of Truck Characteristics as Factors in Roadway Design. Washington, DC: The National Academies Press. doi: 10.17226/23379.
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Suggested Citation:"Appendix B - Weigh Station Data Collection." National Academies of Sciences, Engineering, and Medicine. 2003. Review of Truck Characteristics as Factors in Roadway Design. Washington, DC: The National Academies Press. doi: 10.17226/23379.
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Page 128
Page 129
Suggested Citation:"Appendix B - Weigh Station Data Collection." National Academies of Sciences, Engineering, and Medicine. 2003. Review of Truck Characteristics as Factors in Roadway Design. Washington, DC: The National Academies Press. doi: 10.17226/23379.
×
Page 129
Page 130
Suggested Citation:"Appendix B - Weigh Station Data Collection." National Academies of Sciences, Engineering, and Medicine. 2003. Review of Truck Characteristics as Factors in Roadway Design. Washington, DC: The National Academies Press. doi: 10.17226/23379.
×
Page 130
Page 131
Suggested Citation:"Appendix B - Weigh Station Data Collection." National Academies of Sciences, Engineering, and Medicine. 2003. Review of Truck Characteristics as Factors in Roadway Design. Washington, DC: The National Academies Press. doi: 10.17226/23379.
×
Page 131
Page 132
Suggested Citation:"Appendix B - Weigh Station Data Collection." National Academies of Sciences, Engineering, and Medicine. 2003. Review of Truck Characteristics as Factors in Roadway Design. Washington, DC: The National Academies Press. doi: 10.17226/23379.
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Page 132

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B-1 APPENDIX B WEIGH STATION DATA COLLECTION This appendix discusses the data collection activities con- ducted at weigh stations to gather data on trailer length, rear overhang, and the usage of antilock brake systems (ABS) in the existing truck population. Data collection activities were performed during spring 2002 at three weigh stations in the states of Kansas, Texas, and Missouri. Data were collected over a period of two days at each weigh station. This appen- dix discusses the primary objectives for the weigh station data collection activities, the locations of the weigh stations, the data collection procedures, and the analysis of the field data. The goal of the weigh station data collection activities was to obtain a better understanding of the characteristics and composition of the current U.S. truck fleet, focusing on data elements that were not readily available in existing sources. In particular, information on trailer length, rear overhang, and ABS usage was sought. The primary objectives were to document the following: • The proportion of single-semitrailer trucks with trailers over 16.2 m [53 ft] in length; • The distribution of rear overhang lengths; and • The percentage of trailers with ABS. This information was needed for use in decisions concerning potential changes to design vehicle dimensions and for eval- uating sight distance/deceleration issues. WEIGH STATION LOCATIONS Information on the locations of the weigh stations where the data collection activities were conducted is summarized in Table B-1. The three weigh stations where data were collected are located in the states of Kansas, Texas, and Missouri. Weigh stations in these respective states were selected for specific rea- sons. Missouri was included because the state does not gener- ally allow trucks with trailers longer than 16.2 m [53 ft]; such vehicles can only operate legally with a permit. Kansas and Texas were selected because they do allow trailers over 16.2 m [53 ft] in length to operate on all state highways without a per- mit; the maximum trailer length in Kansas is 18.1 m [59.5 ft], and the maximum trailer length in Texas is 18.0 m [59 ft]. The specific weigh stations in Kansas and Texas were selected, in consultation with these states, at locations that were consid- ered most likely to have truck trailers over 16.2 m [53 ft] in length. The Kansas site was located between Wichita and the Oklahoma state line; Oklahoma also permits trucks up to 18.2 m [59.6 ft] in length. The Texas site was located on a major intrastate trucking route between Houston and Dallas. DATA COLLECTION PROCEDURES Three types of data were collected at each weigh station for the trailers of combination trucks: • Trailer length, • Rear overhang, and • Antilock brakes. Trailer length and rear overhang were measured while each truck stopped on the scales to be weighed. As a truck approached the scale, one data collector was positioned near the rear of the trailer with a measuring wheel, and one data collector was positioned near the front of the trailer. When the truck came to a complete stop, the data collector posi- tioned near the front of the trailer marked, with his foot, the location of the front of the trailer, and the data collector at the rear of the trailer began measuring from the rear bumper of the trailer to the center of the rear axle group, to obtain the rear overhang, and continued measuring to the front of the trailer to obtain the full length of the trailer (Figure B-1). The data collector positioned near the front of the trailer recorded both lengths. The only exception to this procedure relates to mea- surement of the trailer length and rear overhang for automo- bile transport trucks (auto carriers). Since this type of trailer often carries vehicles that extend beyond the rear bumper, the trailer length and rear overhang were measured from the rear- most portion of the vehicles being transported to the front of the trailer. To obtain an accurate measurement of the trailer length and rear overhang, a truck needed to be stopped for approx- imately 5 seconds. At the weigh scales in Missouri and Texas, it is common procedure to have trucks come to a complete stop on the scales to be weighed, so the data collection pro- cedures did not disrupt the normal scale operations. How- ever, at the weigh station in Kansas, trucks typically roll through the scale at speeds of approximately 8 km/h [5 mph], but the scale operators were very cooperative and had trucks come to a complete stop so measurements could be made for this research. In Missouri and Texas, not all trucks that enter the weigh station proceed through the scales. As trucks approach the facilities, they pass over weigh-in-motion scales. Based on their readings, trucks are instructed via traffic signals to either bypass the static scales or proceed to the static scales. This process can be manually overridden by the scale operators to either bypass all vehicles or to weigh all vehicles. Trailer lengths and rear overhangs were measured only for those

trucks that were instructed by the scale operator to proceed to the static scales. A large percentage of the trucks that passed over the static scales during the data collection period were measured for this research. In Kansas, the weigh station had a bypass lane, but it was closed during the two-day data collection period so all trucks that entered the weigh station proceeded over the scale. A large percentage of the trucks that passed over the static scales during the data collection period were measured for this research. To collect information on whether a trailer was equipped with ABS, data collectors looked for the presence of an amber light located on the driver’s side of the trailer near the rear. Figure B-2 provides several illustrations of the amber ABS indicators observed on several types of trailers. In Mis- souri, data collectors positioned themselves such that ABS data were collected for all trucks passing through the weigh station, including those in the bypass lane. In Texas and Kansas, ABS data were collected only for vehicles that passed over the scales. In Missouri and Texas, the layout of the weigh stations made it easier and safer for data collectors to measure trailer lengths and rear overhangs on the passenger side of the vehicles. This prohibited simultaneous collection of lengths (trailer lengths and rear overhang) and ABS data because the amber light is located on the driver’s side of the trailer. Therefore, trailer length and rear overhang data were collected during certain periods of each day, while ABS data were collected during different periods. Over the two-day data collection period in Missouri, length data were B-2 collected for approximately 8.5 hours, while ABS data were collected for approximately 3.5 hours. Over the two-day data collection period in Texas, length data were collected for a period of approximately 11 hours, while ABS data were col- lected for approximately 2 hours. In Kansas all three types of trailer data were collected at the same time. Trailer lengths and rear overhangs were mea- sured from the driver’s side of the vehicle, which permitted observation of ABS lights. Approximately 12 hours of data were collected over the two-day period. When recording all three types of trailer data, each vehi- cle was classified according to the truck configuration. Trailer length and rear overhang data were collected for single-semitrailer trucks, but not for double- or triple-semi- trailers nor for single unit vehicles. ABS data were col- lected for single-, double-, and triple-semitrailer trucks, but not for single unit vehicles. When collecting ABS data for double- and triple-semitrailer trucks, the data were recorded separately for each trailer. SUMMARY OF FIELD DATA Table B-2 shows the number of trailers measured that were 16.2 m [53 ft] in length or less and the number of trail- ers greater than 16.2 m [53 ft] in length. The frequency is bro- ken down by truck configuration and state. The last two columns give the total number of trailers measured and the percentage (by row) of trailers greater than 16.2 m [53 ft] in length. In Kansas, a total of 543 trailers were measured, and only 4 trailers (0.7 percent) were greater than 16.2 m [53 ft] in length. In Texas, a total of 524 trailers were measured, and 23 trailers (or 4.4 percent) were greater than 53 ft in length. In Missouri, 1 of 432 trailers (0.2 percent) measured was greater than 53 ft in length. The last two rows of Table B-2 combine the trailer length data for Kansas, Texas, and Missouri and for Kansas and Texas. Combining the trailer length data for Kansas, Texas, and Missouri, a total of 1,499 trailers were measured with 1.9 percent of the trailers being greater than 16.2 m [53 ft] in length. Combining the data for the two states that permit trailers over 16.2 m [53 ft] in length (Kansas and Texas) data, 2.5 percent of the 1,067 trailers were greater than 16.2 m [53 ft] in length. Table B-3 summarizes the trailer length data by configu- ration for all three states. Several points are of interest. First TABLE B-1 Locations of truck weigh stations where field studies were conducted State Location Interstate Direction of travel KS South of Wichita I-35 NB TX North of Houston I-45 NB MO East of Kansas City I-70 EB Figure B-1. Measuring trailer length and rear overhang.

the table shows that van type configurations are the most prevalent on highways. Of the 1,499 trailers measured, 1,026 were vans. Vans had the greatest frequency of trailers greater than 16.2 m [53 ft] in length, but this only accounted for 1.7 percent of van trailers. On the other hand, 21.6 percent of the automobile transporters were greater than 16.2 m [53 ft] in length. Recall that since automobile transporters often have vehicles that extend beyond the rear bumper, trailer length was measured from the rearmost portion of the vehicles being transported to the front of the trailer. The other types of configurations that had trailers greater than 16.2 m [53 ft] in length were flat beds (2 trucks) and low boy (1 truck). Table B-4 presents the rear overhang data by configura- tion and by state. The rear overhang data are categorized into groups of 1.2-m [4-ft] intervals. In all three states, most of the trailers had a rear overhang of between 1.2 to 3.6 m [4 to 12 ft]. B-3 Table B-5 presents the ABS data by truck configuration and by state. The table shows the total number of trailers with ABS, the total number without ABS, the total number of trailers observed, and the percentage of trailers with ABS. In Kansas, approximately 39 percent of the trailers were equipped with ABS. In Texas, approximately 37 percent of the trailers were equipped with ABS. In Missouri, approxi- mately 46 percent of the trailers were equipped with ABS. In all three states combined, approximately 43 percent of the trailers were equipped with ABS; if equal weight is given to the data from each state, the average ABS penetration for truck trailers is 41 percent. Table B-6 summarizes the ABS data by configuration for all three states combined. Van trailers had the highest percentage (49 percent) of trailers equipped with ABS, while triple trailers had the lowest percentage (16.7) of trailers equipped with ABS. However, it should be noted Figure B-2. Amber ABS indicators.

B-4 TABLE B-2 Frequency of trailer greater than 53 ft in length by truck configuration and by state State Configuration Number of trailers 53 ft in length or less Number of trailers greater than 53 ft in length Number of trailers measured Percentage of trailers greater than 53 ft in length Van 348 2 350 0.6 Flat Bed 104 0 104 0.0 Grain 17 0 17 0.0 Tanker 35 0 35 0.0 Low Boy 7 0 7 0.0 Auto 10 2 12 16.7 Other 18 0 18 0.0 KS Totals 539 4 543 0.7 Van 317 15 332 4.5 Flat Bed 99 2 101 2.0 Grain 4 0 4 0.0 Tanker 44 0 44 0.0 Low Boy 9 1 10 10.0 Auto 7 5 12 41.7 Other 21 0 21 0.0 TX Totals 501 23 524 4.4 Van 344 0 344 0.0 Flat Bed 34 0 34 0.0 Grain 12 0 12 0.0 Tanker 19 0 19 0.0 Low Boy 8 0 8 0.0 Auto 12 1 13 7.7 Other 2 0 2 0.0 MO1 Totals 431 1 432 0.2 Total for All 3 States 1471 28 1499 1.9 Totals for KS & TX 1040 27 1067 2.5 1 Trailers over 53 ft in length are not permitted to operate on Missouri highways without a permit. TABLE B-3 Frequency of trailers greater than 53 ft in length by truck configuration Configuration Number of trailers 53 ft in length or less Number of trailers greater than 53 ft in length Number of trailers measured Percentage of trailers greater than 53 ft in length Van 1009 17 1026 1.7 Flat Bed 237 2 239 0.8 Grain 33 0 33 0.0 Tanker 98 0 98 0.0 Low Boy 24 1 25 4.0 Auto 29 8 37 21.6 Other 41 0 41 0.0 Totals 1471 28 1499 1.9 NOTE: Data for all three states combined.

B-5 Length of rear overhang State Configuration 0 - 4 ft 4 - 8 ft 8 - 12 ft 12 - 16 ft 16 - 20 ft 20 - 24 ft Total Van 2 79 217 54 0 0 352 Flat Bed 1 76 24 3 0 0 104 Grain 5 11 1 0 0 0 17 Tanker 8 27 0 0 0 0 35 Low Boy 3 3 0 1 0 0 7 Auto 1 3 1 3 4 0 12 Other 5 12 1 0 0 0 18 KS Totals 25 211 244 61 4 0 545 Van 7 68 150 79 1 0 335 Flat Bed 1 67 28 5 0 0 101 Grain 1 3 0 0 0 0 4 Tanker 1 41 0 2 0 0 44 Low Boy 0 8 0 2 0 0 10 Auto 0 0 0 4 7 1 12 Other 4 14 1 1 1 0 21 TX Totals 14 201 209 93 9 1 527 Van 1 77 204 61 0 0 343 Flat Bed 0 21 12 1 0 0 34 Grain 8 4 0 0 0 0 12 Tanker 5 14 0 0 0 0 19 Low Boy 2 2 2 2 0 0 8 Auto 0 1 1 4 7 0 13 Other 1 0 0 1 0 0 2 MO Totals 17 119 219 69 7 0 431 Total for All 3 States 56 531 672 223 20 1 1503 Percentage of Totals 3.73 35.33 44.71 14.84 1.33 0.07 TABLE B-5 Frequency of trailers with ABS by configuration and by state State Trailer configuration Number of trailers with ABS Number of trailers without ABS Number of trailers observed Percent of trailers with ABS Van 161 190 351 45.9 Flat Bed 36 67 103 35.0 Grain 7 11 18 38.9 Tanker 11 27 38 29.0 Low Boy 2 5 7 28.6 Auto 1 8 9 11.1 Double 4 20 24 16.7 Triple 2 10 12 16.7 Other 5 13 18 27.8 KS Total 229 351 580 39.5 Van 35 50 85 41.2 Flat Bed 9 14 23 39.1 Grain 1 0 1 100.0 Tanker 4 11 15 26.7 Low Boy 0 3 3 0.0 Auto 3 2 5 60.0 Double 4 10 14 28.6 Triple 0 0 0 0.0 Other 2 9 11 18.2 TX Total 58 99 157 36.9 Van 261 239 500 52.2 Flat Bed 27 47 74 36.5 Grain 6 14 20 30.0 Tanker 4 19 23 17.4 Low Boy 2 4 6 33.3 Auto 7 6 13 53.9 Double 21 39 60 35.0 Triple 0 0 0 0.0 Other 2 14 16 12.5 MO Total 330 382 712 46.4 Total for All 3 States 617 832 1449 42.6 TABLE B-4 Frequency of rear overhang length by truck configuration and by state

that the sample size of triple trailers was small (12 trailers observed). The field data presented in Tables B-2 through B-6 provide useful data to characterize the current truck population. In the two states that permitted longer trailers, only approximately 2.5 percent of the trailers measured were, in fact, over 16.2 m B-6 [53 ft] in length. This does not suggest a current need to include a design vehicle with a trailer length greater than 16.2 m [53 ft] in the Green Book. The field data on trailer lengths and rear overhangs was considered in the offtracking investigation (see Appendix C). Finally, the field data suggest that the ABS pen- etration in the trailer population is approximately 42 percent. TABLE B-6 Frequency of trailers with ABS by truck configuration Trailer configuration Number of trailers with ABS Number of trailers without ABS Number of trailers observed Percent of trailers with ABS Van 457 479 936 48.8 Flat Bed 72 128 200 36.0 Grain 14 25 39 35.9 Tanker 19 57 76 25.0 Low Boy 4 12 16 25.0 Auto 11 16 27 40.7 Double 29 69 98 29.6 Triple 2 10 12 16.7 Other 9 36 45 20.0 Total 617 832 1449 42.6 NOTE: Data for all three states combined.

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TRB’s National Cooperative Highway Research Program (NCHRP) Report 505: Review of Truck Characteristics as Factors in Roadway Design presents guidance to roadway geometric designers on how to accommodate large trucks on the U.S. highway system.

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