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(1)
Horsepower rating of powerplant in relation to car speed, weight, grades, curvature and operating schedules; especially in the case of internal-combustion engines the power must be sufficient to permit engine operation at speeds and outputs well within the maximum of the engine
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(2)
Type of transmission between engine and wheels; to be simple to operate, accessible for repairs, rugged for endurance, quiet in operation and efficient in power transmission
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(3)
Single-end versus double-end control; the former is far preferable if terminal conditions permit, because it is cheaper to build, more reliable, has less weight and is easier to operate
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(4)
Distribution of available space between engine room, baggage room and passenger compartment. This factor is largely variable according to the ideas and the needs of the carrier. However, the convenience, comfort and safety of the passengers and the convenience of the crew require consideration because of the space available and the permissible weight
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(5)
Materials of construction are important and largely different from those usual in railroad equipment construction. Care is necessary to give lightness, strength, warmth, good appearance and quietness of operation at a permissible cost. Climatic conditions should be considered, as well as the more or less exacting requirements of the particular service
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(6)
Design of the car frame and body and of the trucks to give strength, lightness, good appearance and safe and quiet operation needs careful study and departure largely from usual steam-road practices
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(7)
Heating, signaling, lighting, ventilation and braking are all important factors concerning which experience has produced much information
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(8)
Multiple-unit control may be of some importance in later developments for specialized service but does not appear to be of considerable moment