ACCELERATION AND DECELERATION CHARACTERISTICS OF PRIVATE PASSENGER VEHICLES

A STUDY HAS BEEN MADE TO DETERMINE MAXIMUM ACCELERATION FOR PASSENGER CARS AND THEIR FREEWHEELING AND HIGH-GEAR DECELERATION UNDER TEST CONDITIONS. INVESTIGATION WAS ALSO MADE OF ACCELERATION AND DECELERATION UNDER RUNNING CONDITIONS. TEST CARS WERE USED IN THE FIRST INSTANCE, WITHOUT OVERHAUL OR SPECIAL 'TUNE-UP', WHILE IN THE SECOND INSTANCE CARS WERE OBSERVED UNDER NORMAL DRIVING CONDITIONS, WITHOUT THE KNOWLEDGE OF THE OPERATORS. SECOND AND HIGH-GEAR MAXIMUM ACCELERATION OBTAINED FROM THE TEST CARS WERE APPROXIMATELY SIMILAR, APPROACHING A MAXIMUM AT SPEEDS BETWEEN 15 AND 25 M.P.H. FOR SECOND GEAR AND BETWEEN 20 AND 35 M.P.H. FOR HIGH GEAR, WITH AN APPROXIMATE STRAIGHT-LINE DECREASE TO ZERO AT MAXIMUM SPEED. HIGH-GEAR DECELERATION IS AFFECTED BY THE SAME FORCES AFFECTING FREE-WHEELING DECELERATION, BUT WITH THE ADDITIONAL FACTOR OF FRICTION AND COMPRESSION OF THE MOTOR, DECELERATION INCREASED WITH SPEED. AT A RATE GREATER THAN THE FIRST POWER OF THE SPEED, AIR RESISTANCE BEING THE MOST RESPONSIBLE FACTOR. REGARDING OBSERVATIONS OF DECELERATION, ONLY VEHICLES TRAVELING AT THE HIGHER SPEEDS EXCEEDED A RATE OF DECELERATION OF 8 M.P.H. PER SEC., AND 9 MP.PH. PER SEC. APPEARS TO BE THE MAXIMUM WITHOUT DISCOMFORT TO PASSENGERS. ACCELERATION CURVES ARE SIMILAR IN SHAPE TO DECELERATION CURVES, EXCEPT THAT THE ORDINATE VALUES ARE BUT HALF OF THOSE FOR DECELERATION. A HIGH RATE OF ACCELERATION IS USED FOR A SHORT DISTANCE FROM THE STARTING POINT, DECREASING AT A GRADUAL RATE AFTER SHIFTING INTO HIGH. THIS SHIFT OCCURS BETWEEN 100 AND 200 FT. FROM THE STARTING POINT, WITH DRIVERS IN THE LOWER SPEED GROUPS SHIFTING INTO HIGH GEAR SOONER AND USING A LOWER RATE OF ACCELERATION. /AUTHOR/