d
rubber tires on asphalt and bitulithic, wood, brick and granite block,
water-bonded and tar macadam, cinder and gravel road surfaces were
obtained by A. E. Kennelly and O. R. Schurig in the research division
of the electrical engineering department of the Massachusetts
Institute of Technology, and are published in Bulletin No. 10 of the
division.

An electric truck was run over measured sections, ranging from 400 to
2600 feet in length, surfaced with these various materials, at certain
speeds per hour, ranging from about 8 to about 15.5 miles per hour.
The result of the observations of speeds, tractive resistances,
conditions of surfaces, etc., were collected and studied in various
combinations.

TABLE 6

----------------------+-----------------------+-----------+----------
| | Tractive | Tractive
| |Resistance |Resistance
Type of Surface | Condition of Surface | in lbs. | in lbs.
| | per ton | per ton
| | 10 miles |12.4 miles
| | per hr. | per hr.
----------------------+-----------------------+-----------+----------
Asphalt | Good | 20.4 |
Asphalt | Poor | 22.6 | 25.5
Wood block | Good | 24.2 | 25.3
Brick block | Good | 24.6 | 26.6
Granite block | Good | 40.3 | 45.75
Brick block | Slightly worn | 25.1 | 28.0
Granite block with | | |
cement joints | Good | 25.5 | 30.2
Macadam, water bonded | Dry and hard | 23.3 | 25.8
Macadam, water bonded | Fair, heavily oiled | 35.9 | 38.7
Macadam, water bonded | Poor, damp, some holes| 36.3 | 41.6
Tar macadam | Good | 25.7 | 28.0
Tar macadam | Very soft | 36.8 | 38.7
Tar macadam | Many holes, soft, | |
| extremely poor | 52.4 | 60.6
Cinder | Fair, hard | 27.5 | 30.6
Gravel | Fair, dusty | 30.4 | 33.0
------------