EFFECT OF LENGTH OF GRADE ON SPEED OF MOTOR VEHICLES
IN 1942, THE PUBLIC ROADS ADMINISTRATION PUBLISHED THE RESULTS OF EXTENSIVE STUDIES ON THE HILL-CLIMBING ABILITY OF MOTOR TRUCKS AND TRACTOR-TRUCKS WITH SEMITRAILER COMBINATIONS IN VARIOUS STAGES OF USAGE AND WEAR. USING THE VEHICLE PERFORMANCE AND TRACTIVE RESISTANCE DATA FROM THIS REPORT, THE EFFECT OF THE LENGTH OF GRADE ON THE SPEED OF MOTOR VEHICLES WAS DETERMINED FOR A WIDE RANGE OF LOAD, GRADE, AND VEHICLE SIZE. THE RESULTS WERE CHECKED WITH EXHAUSTIVE DATA COLLECTED IN THE FIELD FOR A RATHER LIMITED SET OF CONDITIONS. THE GRADE ABILITY OF MOTOR VEHICLES FOR VARIOUS SUSTAINED SPEEDS IS REDUCED TO TRACTIVE EFFORT. THE TRACTIVE EFFORT ADDED TO THE ENERGY SUPPLIED DUE TO VEHICLE MOTION (KINETIC ENERGY) IS EXPENDED AGAINST THE GRADE AND TRACTIVE RESISTANCE. A FORMULA IS THEN DEVELOPED BY WHICH CALCULATIONS ARE MADE TO DETERMINE THE LENGTH OF GRADE THAT A MOTOR TRUCK TRAVELS DURING A GIVEN SPEED INTERVAL. THE RESULTS ARE SHOWN BY GRAPHS FOR LIGHT, MEDIUM, AND HEAVY VEHICLES WITH GROSS LOADS UP TO 40,000 LB., FOR OPERATION ON GRADES OF 2 TO 7 PERCENT. MOMENTUM OF THE VEHICLES, PRINCIPALLY AT SPEEDS ABOVE 30 MILES PER HOUR, ACCOUNTS FOR A CONSIDERABLE PORTION OF THE TOTAL ENERGY AVAILABLE IN OVERCOMING GRADES. IT WAS FOUND, FOR EXAMPLE, THAT IF VEHICLES, REGARDLESS OF THE GROSS LOAD, COULD APPROACH GRADES AT 40 M.P.H. WITH THE ENGINE DISENGAGED, A SPEED OF 20 M.P.H. WOULD BE REALIZED AT THE TOPS OF 3- AND 7-PERCENT GRADES 1,000 AND 500 FT. LONG, RESPECTIVELY. UTILIZING THE POWER OF THE ENGINE , A TYPICAL VEHICLE WITH 30,000 LB. WOULD REACH THE TOPS OF THESE GRADES AT SPEEDS OF 32.5 AND 27.7 M.P.H. RESPECTIVELY. /AUTHOR/
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Supplemental Notes:
- Vol 25, pp 342-353, 12 FIG, 3 TAB. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved.
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Authors:
- Taragin, A
- Publication Date: 1946
Media Info
- Media Type: Digital/other
- Monograph Title: Proceedings of the Twenty-Fifth Annual Meeting Held at Skirvin Hotel, Oklahoma City, Oklahoma, January 25-28, 1946
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Serial:
- Highway Research Board Proceedings
- Volume: 25
- Publisher: Highway Research Board
Subject/Index Terms
- TRT Terms: Kinetic energy; Length; Slopes; Speed; Tractive forces; Vehicles
- Uncontrolled Terms: Grade (Slope)
- Subject Areas: Highways; Safety and Human Factors; Vehicles and Equipment;
Filing Info
- Accession Number: 00223496
- Record Type: Publication
- Files: TRIS, TRB
- Created Date: Jun 22 1971 12:00AM