| 49.2
| surface | | |
| asphaltic oil | | |
| and screenings| | |
13-14 | Concrete 3/8-in.|Good, excellent | 155.0 | 51.6
| surface | | |
| asphaltic oil | | |
| and screenings| | |
9-10 | Macadam, |Good, excellent | 193.0 | 64.3
| water-bound | | |
22-23 | Topeka on |Good, excellent | 205.5 | 68.5
| concrete | | |
8 | Gravel |Compact, good | 225.0 | 75.0
| | condition | |
[3]45-48 | Oil macadam |Good, new | 234.5 | 78.2
[4]46-47 | Oil macadam |Good, new | 244.0 | 81.3
38 | Gravel |Packed, in | 247.0 | 82.3
| | good condition | |
18-19-20 | Topeka on plank |Good condition, | 265.0 | 88.3
| | soft, wagon | |
| | left marks | |
34 | Earth road |Firm, 1-1/2-in. | 276.0 | 92.0
| | fine loose dust| |
24-25 | Topeka on plank |Good condition, | 278.0 | 92.6
| | but soft | |
1-2-5 | Earth road |Dust 3/4 to 2 in.| 298.0 | 99.3
3-3 | Earth |Mud, stiff, firm | 654.0 | 218.0
| | underneath | |
6-7 | Gravel |Loose, not packed| 789.0 | 263.0
----------+-----------------+-----------------+-----------+-----------

[1] Prof. J. B. Davidson in _Engineering News-Record_, August 17,
1918.

[2] Graphic record indicates that the load was being accelerated
when test was started.

[3] Drawn with motor truck at 2-1/2 miles per hour.

[4] Drawn with motor truck at 5 miles per hour.

Comparatively few data are available showing the tractive resistance
of motor vehicles, but the following tables are based on sufficient
data to serve to illustrate the general trend.

These data on the tractive resistances of an electric truck with soli