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mmunum turning radius of less than fifty feet should not be used. 2. The maximum angle of turn, inside wheel, which will be valid for most vehicles is 300. 3. A general dimension for track is 77 inches when maximum vehicle width does not exceed 96 inches. For vehicles exceeding 96 inches over-all width, add an inch to track for each inch of width in excess of 96. Track for 102 inches over-all width = 77 + (102.96) = 83. Pages 16 thru 18 present methods of determining straight truck or tractor turning radius. Page 16 gives three separate methods of determining the turning radius, and pages 17 and 18 are charts needed for the last of those three methods. The first two methods of determining straight truck or tractor turning radius shown on page 16 are strictly mathematical approaches and involve direct calculation of the turning radius (TR). The third method is some- what simpler and faster in that it only involves picking a number from the graph on page 17 and a number from the graph on page 18, then adding the two. Page 17 is a plot of the relationships between wheel- base and turning radius given in the first two proce- dures shown on page 16. Page 18 is a plot of cor- rections needed to adjust values from page 17 for vehicles with track wider than 65 inches. The points plotted for page 18 were not absolutely linear; hence, there is a small degree of error inherent in page 18. Track plots With vehicle size and straight truck or tractor turning radius determined it is possible to construct the turning track plots_ Pages 19, 20, 21, 22, and 23 present the procedure. For a tractor-semitrailer this procedure con- sists of two parts: (1) tractor turning track plot (pages 19, 20, and 21) and (2) semitrailer turning track plot (pages 22 and 23). Page 19 shows the first steps necessary in construct- ing a tractor-semitrailer or straight truck turning track plot. This sheet is basically a turning circle made with the straight truck or tractor turning radius determined from pages 16, 17 and 18 and divided at the degrees of turn of interest. For the example, the turning circle was divided at 900, 1800, 2700 and 3600. It should be noted that the circle can be divided, and the turning track plot made, for any degree of turn of interest, not just those shown in the example. On page 20 the turning circle from page 19 is ex- panded by adding a sketch of (1) the wheelbase, track, front bumper, and fifth wheel pivot center1 of the sub- ject tractor [as in the example] or (2) a complete top view of the subject straight truck [see page 24]. Page 21 gives the fmal steps necessary in constructing a turning track plot for either a truck-tractor or a straight truck. On this sheet the subject vehicle is moved through the degree of turn of interest and its track through that turn is traced. The method of constructing a straight truck or tractor turning track plot described traces, throughout the total turning range, a turning track incorporating the maximum off track which can be generated by the vehicle. Although the maximum off- track a vehicle can generate is not reached during every turn and for larger vehicles usually does not occur until about 2700 of turn, for straight trucks and tractors with wheelbase (WB) lengths of 25 feet and less, the error in track size introduced by plotting only maximum off- track is slight. For straight trucks and tractors in that length range, off track for any turn approaches the maxi- mum. For straight trucks of over 35 feet in length (25 ft. wheelbase), the error begins to get excessive for small degrees of turn and a method similar to that for semi- trailers should be used to construct the straight truck turning track plot. Page 22 and part of page 23 present the procedure for constructing the semitrailer turning track plot. The base line for this plot is the fifth wheel pivot center turning circle. This pivot center was plotted in the tractor proce- dure described on pages 19, 20 and 2 L Doubles and Truck-Full Trailer Vehicles On page 23, the procedure for plotting the turning track path of doubles and truck-full trailer vehicles is given along with a sketch of those two vehicles. Examples Following are: (1) some examples of the turning track paths of different vehicles for various types of turn (pages 24, 25, 26, and 27),(2) a method of determining needed pull-out space (page 29), and (3) plots of the equation from SAE J695 (1969 SAE Handbook), show- ing maximum off track for a given turning radius (pages 30 through 33). It should be noted that the examples are included mainly to show what can be done with the track plot procedures. Although the vehicles in the examples do represent vehicles which could be in com- mon use today, as size and weight regulations change, vehicles with entirely different configurations may corne into general usage. It should also be noted that the pro- cedure presented herein is a method of approximating I The fifrh wheel pivot center is that point where the semitrailer is coupled to the tractor. The coupling is accomplished by inserting and clizmping the semitrailer kingpin in the tractor coupler (fifth wheel) jaws. 6