Arizona republican., 1921-02-20

Washington has conducted extensive experiments in order to determine the type of highway which will give the largest number of miles of load ability per dollar expended-- the other phase of the prob lem-that of regulating motor vehicles so as to ge the greatest tonnage trans ported with the least damage to the roads presents much greater difficul- ties. since the decision rests, not in the hands of a centrally located group Of technically informed men, but with nu- merous widely scattered legislative bodies. The ineffectiveness of this ar rangenient can be seen by the fact that methods of restricting motor vehicles vary widely in all parts of the country.
 While it is certain that every legis- lature passing a law to establish H- cense fees or restrict traffic, does so in an earnest effort to conserve the roads. there is strong tendency on the part of those not fully apprised of real facts to assume that small trucks cause less road wear than large trucks and that they should therefore be favored.
 Consider for a moment the effect of legislation that has favored the lighter capacity truck. Regardless of whether the material is to be shipped in large or small trucks, the demand for truck transportation remains the same, as practically none of it can be diverted to other channels. As d result. when large unit hauIage is discouraged, the same amount of freight is merely divided up among a greater number of smaller ve
 hicles. running at far greater speeds and increasing the cost of hauling by very considerable percentage.
 If this decreased the amount of road wear and permitted our SS00,00 900 f7as cry ont n nh load carrying ability, it is possible that the increased cost would be justified. But this is not the case 4 careful consideration of the effect clearly shows that to substitute smaller trucks for large one, unquestionably increases road wear. To illustrate,-suppose each dollar spent in highway Improvement as an arbitrary figure, buys 1000 ton miles of load carrying ability. Bearing in mind that two kinds of weight travel over these roads-weight of load and weight of Vehicle-it is obvious that the dividends on our investment will i be determined by the proportion of this traffic which is useful weight--of weight of load The F ton truck has ] less than one ton of vehicle weight for 1 each ton of capacity; hence, ii all tho I vehicles operating over this dollar $ worth of highway were of l@-tons capacity, then that dollar would pro , transportation. A 1-ton truck, on the other hand, ordinarily weighs over two 4 tons itself and so if this size were used I entirely. the same dollars worth of road would give only 333 ton miles ot
 useful load transportation as two
 thirds of the roads carrying ability | would be used in transporting the
 weight of the truck
 l The design of the vehicle, as well as
 size. has an important bearing on the i potential returns of our $S00,e00,000 in- | vestment. Certain tests conducted by the Bureau of Public Roads at Wash ington show that road impact, which is the principal cause of road wear
 does not necessarily increase in propor-
 ton to the size of the truck, but is
 governed by the amount of weigh 1 which truck carries helow it's springs
 For instance, a 515 ton chain drivex
 truck, fully loaded, delivered only 6s
 per cent of the road impact pressure
 produced by a 3-ton shaft-driven truct
 there Is no weight belo wthe spring.
 except that of the wheels and a com
 parativcIy light axle. That is wEsT 2
 IF ton chain driven rtuck win pro
 duce less road impact and consequent, less road wear than a five-ton shaft
 driven~9ruclS. And furthermore, tha
 is why vehicle design should be con considered in framing legislation to de
 
 our $500, ,000 900 highway investment. Unfortunately. this subject of gros weight restriction is too eaisly misun 7 derstood The tendency to jump q | conclusions in determining which type and sizes of motor vehicles exert tn H greatest road wear is very natura S one, owing to the popular confusial between static weight and "impac weight" To be sure. 8 E ton truc standing still is heavier on the roa than q five-ton truck regardless 0 ! whether it is chain or shaft driver 4 But static weight does not wear ou the roads, as was proved by the gov \ ernment tests and as any one ca readily see. It is the constant impaC h i pressure caused by d moving truck X the repetition of shocks or blows-tha R alone affects the road surface and ii K foundation. And it has been conclu X sively proven time and again that fins H drive construction has an exceptional b important bearing on impact pressur that in motion, a 7l2 ton chain \ driven truck produces less impa' E pressure, and consequently less roa E wear than q five-ton shaft-drive K truck. Is il not reasonable, therefor B for the peopleo of this country who al < paying this $500 100000 for highwa k improvement and who are vitally cor cerned in sportation costs as the E affect commodity prices, to demaT ' that legislators apprise themselves the facts concerning motor vehicle d. q sign that will provide method f. both lengthening the life fthe hsl z ways and lowering trausportatiC