OF PAPER In this paper is given a complete report on an investigation of tractive resistances of urban roads to a motor delivery wagon equipped with solid rubber tires. The " tractive resistance " as used in this paper, includes still-air resistance, but does not in clude wind resistance and the resistances internal to the truck. The test truck is fully described with its driving mechanism anâ the storage battery which supplied the motive power. The investigation involved test runs over

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... lengths of road, at measured truck speeds, to determine the gross battery output during these runs; and laboratory tests to determine the overall efficiency of the truck between battery terminals and rear-wheel treads at speeds and loads corresponding to the road tests. The results included in the paper are (1) o\^erall efficiency of truck mechanism and (2) tractive resistances of a number of typical urban roads. The components of tractive resistance for a typical road are also given. ÔÃÇÅ INVESTIGATION herein described was carried on in **· the Research Division of the Electrical Engineering De partment, at the Massachusetts Institute of Technology, during the year 1915, under a fund contributed for researches on motor trucks. Object of the Research. The object of £his research was to determine the resistance, including air resistance, offered to an electric truck, by level urban roads of different surface varieties, at standard truck speeds not exceeding 25 km. (15.5 miles) per hour. For thi,s purpose, the output of the storage battery on a test truck was measured, for both directions of travel, over standard road beds, at different controller speeds. From this output were deducted all the corresponding electrical and mechanical losses in the truck mechanism, as determined by laboratory tests. The remainder of the output was conse quently attributed to (1) road-(2) air-and (3) wind-resistance.