20 
BULLETIN 1259, U. S. DEPARTME:N^T OF AGRICULTURE. 
In all cases involving curved tracks the lateral clear- 
ances shall be increased an amount corresponding to that 
required to maintain the standard clearances. When 
the outer rail is superelevated the clearances shall be 
correspondingly increased. 
trisera^Dd^gird- Main trusscs and girders shall be spaced a sufficient 
ers. " distance apart center-to-center, to be secure against over- 
turning by the assumed lateral and other forces. 
/tCurb 
32'-0 (Not Less)for Single Track 
43-0 (Not Less) for Double Tra.ck- 
Horizontal Clearance 
1 \PA> 
Fig. 4. — Clearance diagram for electric railway and two-way highway traffic 
bridg^T ^ ^ ° ^ The type of bridge to be used for various span lengths 
may be as foUows: 
Rolled beams up to 40 feet. 
Plate girders from 30 to 100 feet. 
Low riveted trusses from 45 to 100 feet. 
Riveted trusses from 90 to 150 feet. 
Riveted or pin-connected trusses above 150 feet. 
SECTION 2. LOADS. 
Unless otherwise provided the component parts of a 
structure shall be proportioned for the stresses produced 
by the following loads with the assumed load distribu- 
tion described in Section 4. The stresses due to each shall 
be shown separately upon stress sheets. 
1. Dead load. rpj^^ dead load shall consist of the weight of the struc- 
tm*e complete, including the weight of the roadway floor, 
conduits, cables, or other public utihty services support-ed 
thereon. 
