HIGHWAY BKIDGE LOCATION 
23 
center of the bridge or as near the center as possible. The length of 
the tangent T should preferably be not less than 200 feet. The camber 
C for this type of grade treatment will be as required by the vertical 
curve and will be the same for all types of construction. The vertical 
curve should not, in general, be shorter than the length of the bridge 
and not less than that required by other standards. For structures 
IdXMXMXMXl^^ 
Fig. 19. — Treatment of grade line where the grades on each side of the vertex are unequal in amount 
but the bridge can be centered under the vertex 
exceeding 800 feet in total length, certain clearance and grade point 
restriction may render it necessary to extend the tangent T partly 
onto the structure. This is to be avoided, however, if it can be 
done without prohibitive cost. 
If it is impossible to lay the approaches on equal grades, a treat- 
ment as shown in Figure 19 may be adopted. This type of grade line 
Fig. 20.— Treatment of grade line where the grades on each side of the vertex are 
ULequal in amount and the bridge can not be centered under the vertex 
should not be used unless absolutely necessary. If impossible to 
center the vertex over the bridge, a treatment as shown in Figure 20 
may be adopted. In this case, the vertical curve may be made 
symmetrical and the bridge placed on an}^ portion of it as shown by 
line B or an unsymmetrical vertical curve may be worked out as shown 
by line A. 
