pf_02608 - Laserfiche WebLink

Home

APPENDIX I TRUCK SIZE AND TURNING TRACK DETERMINATION PROCEDURES The method for determining a vehicle turning track plot to be described within this Appendix is divided roughly into two parts. The first part deals with determining vehicle size and the second with maneuver. ab ility . General vehicle size Pages 11 thru 13 show general types of vehicles used today and the range of some of their dimensions. Those sheets will help one to familiarize himself, somewhat, with equipment presently used by truck operators. The dimensions given should not be considered standards, as they vary according to state law, vehicle type, and brand. Vehicle width One dimension not given on page 13 is width. Cur. rently the maximum width of most vehicles is eight feet (96 inches). Presently, unconditional maximum width (for all types of vehicles without special permits), in all states except three is 96 inches. In Connecticut and Rhode Island, the maximum is 102 inches, and in Hawaii it is 108 inches. It should be noted that in a report from the Bureau of Public Roads of the United States Depart. ment of Commerce1, widths of 102 inches were consid. ered acceptable. In designing facilities which will be used for several years, then, it might be wise to consider 102 inches as maximum vehicle width. Maximum width has been assumed to be 96 inches throughout the procedure presented in this Appendix. State laws governing vehicle width have a clause in them which reads generally, uMaXimum vehicle width, excluding, safety equipment, shall be X feet." Safety equipment may include such things as lights and reo flectors. One thing it always includes are the vehicle's mirrors. Mirrors obviously have to extend beyond the width of the vehicle. At their position on the vehicle, the mirrors, together, add about l' 8" to total vehicle width. At the mirror, then, an 8-foot (96=inch) vehicle would be about ten feet wide. Dimension determination Pages 14 and 15 give relationships which. coupled with data available from state size and weight laws, enable I "Maximum Desirable Dimensions and Weighrs of Vehicles Operated on the Federal A id Sysrems, " Report Pursuant to Section 108 (K) of the Federal Aid Highway Act of 1956. u. S. Dept. of Commerce. Bureau of Public Roads. August. 1964. one to determine . the vehicle dimensions necessary to construct a turning track plot for the tractor.semitrailer which generates maximum tr~ck. The relationships given on page 15 for determining tractor wheelbase (WB) and kingpin offset (Of) are based on the physical relation- ships which must exist to distribute the combined weight of the payload and vehicle in such a manner that state laws g.overning maximum axle loads are not exceeded. Size and weight information necessary can be ob- tained from the uSummary of Size and Weight Limits" chart. The data which can be determined directly from the size and weight chart are (I) combination total length (OL), given on the chart as uT.S.T.;' and (2) semitrailer total length (S), given on the chart as "Trailer or Semi.Trl." The other values that are necessary for determining the tractor wheelbase (WB) of the tractor-semitrailer which generates the largest turning track are (1) the pay- load carried on the tractor front axle (F AU. and (2) the payload (TL) carried on the tractor rear axles (bogie). Payload is the weight of cargo, or total loaded weight of the vehicle, minus the unloaded (empty) vehicle weight. To determine FAL and TL it has been assumed (1) that the minimum total front axle load on a tractor. semitrailer, loaded to the highest weight possible in a particular state, is 9280 lbs., and (2) that the portion of the total load not carried on the tractor front axle is carried half by the tractor rear axles (tractor bogie) and half by the semitrailer rear axles (semitrailer bogie). In general, the procedure for determining FAL and TL entails finding (1) the actual maximum total load which can be carried on the tractor front axle, tractor bogie, and semitrailer bogie and (2) determining FAL and TL by subtracting from the maximum total front ax.le and tractor bogie loads the portion of the weight of the unloaded vehicle each axle or axle group carries. I t has been assumed that the unloaded vehicle weight carried (I) on the tractor front axle is 7900 Ibs. (7800 Ibs. for the unloaded tractor plus 100 Ibs. for the unloaded semi. trailer), and (2) on the tractor bogie is 9300 Ibs. (6200 Ibs. from the unloaded tractor plus 3100 lbs. from the unloaded semitrailer). Turning radius After determining the size of vehicle to be analyzed, the next data necessary for making a turning track plot is to determine the minimum turning radius of the sub- ject straight truck or tractor. Some general rules for turning radius determination follow: 1. Whenever the velocity of a combination vehicle (tractor.semitrailer. doubles, truck. full trailer) will exceed three miles per hour during a turn, a