18 
BULLETIN 1259, U. S. DEPARTMEXT OF AGRICULTURE. 
DIVISION III. DESIGN. 
1. Width of 
roadway and 
sidewalk. 
2. Curbs. 
SECTION 1. GENERAL FEATURES. 
The width of roadway shall be the clear width measured 
at right angles to the longitudinal center line of the bridge 
between the tops of curbs or guard timbers, if these 
exist; otherwise it shall be the clear ^^ddth inside-to- 
inside of the handrails or other fencelike protections 
paralleling the sides of the structure. 
Upon structures having a sidewalk, the clear width of 
sidewalk shall be measured at right angles to the curb or 
guard timber and from the face thereof to the extreme 
inside portion of the handrail. For structm-es having 
trusses, gu'ders, or parapet walls adjacent to the curbs 
the width of sidewalk shall be measured from their ex- 
treme outside portions to the inside of the handrail. 
The width of curbs shall be not less than 6 inches and 
preferably shall be not less than 9 inches. Their height 
shall be not less than 9 inches. 
3-°7 
6-0 
s^: 

(Not Less) 
,3'-C 
/ 
\ 
\ 
8 
Curb-^ 
^h — Roadway 
,9 
-Curb 
^s^ 
% 
O 
2 
s 
15 
o 
t 
^ 
i 
t 
Curb 
-Tr- 
'Crown 
t^ll'-O (Nor Less)-* 
12-0 (Not Less) 
w> 
Hori2 
ontal Clear 
-a nee 
Fig. 1.— Clearance diagram for one-way highway traffic 
3. Clearances. The clearance width shall be the clear width available, 
and the clearance height shall be the clear height avail- 
able, for the passage of vehicular traffic, as shown on the 
clearance diagrams. 
Unless othei'wise provided the several parts of the 
structure shall be constructed to secure the following 
limiting dimensions or clearances for traffic. 
Bridges constructed for the use of 6ne-way highway 
traffic shall have a roadway clearance not less than that 
shown in Figure 1. The roadwav clearance for the use 
