HIGHWAY BRIDGE LOCATION 21 
public will continue to pay the penalty indefinitely. The feeling is 
prevalent among engineers that massive concrete work will last for 
many centuries. In building this type of substructure, therefore, the 
location problem becomes a paramount issue and should be given 
much more study than has often been the case in times past. 
Plate 5, B illustrates the tendency, so frequently observed, to utterly 
disregard considerations of traffic service and safety and to place the 
bridge structure with regard for but one consideration — viz, low 
first cost. 
GRADE-LINE TREATMENTS 
The grade line adopted for any highway bridge structure has an 
important bearing on its utility and appearance, more especially the 
latter. There are certain things which can be done and, from the 
standpoint of appearance, certain things which can not be done with 
a bridge grade line. In rolling country practically every other vertical 
curve will be concave upwards. On the highway proper this treat- 
ment is not objectionable in appearance and unless drainage conditions 
interpose may be considered good practice. On bridge structures, 
however, a concave grade line invariably presents the appearance 
of sag in the railing and weakness in the structure. It is, therefore, 
highly desirable that grades be so chosen as to approach the structure 
proper from each direction on an ascending grade. In general, it has 
been found that camber on bridges can be introduced more effec- 
tively by springing a long vertical curve from end to end of the struc- 
ture than by the use of any fixed camber diagram or table. 
It is also desirable to have the approaching grade lines intersect at 
a point as near as possible to the center of the bridge in order to make 
the appearance symmetrical. The elimination of concave vertical 
curvature is doubly necessary in cases where the horizontal align- 
ment is not all tangent. It is impossible to combine inverse or con- 
cave vertical curvature with horizontal curvature without entirely 
ruining the appearance of the structure. No matter how straight 
and true the alignment of the handrail, the concave or inverse ver- 
tical curve in combination with the horizontal curve will introduce an 
optical illusion of reverse curvature in the railing, so that the 
appearance of the structure is completely ruined. More and more 
are engineers and public officials coming to appreciate the necessity for 
pleasing and correct aesthetic or architectural treatment in highway 
construction. For bridge structures, the appearance depends on the 
structural fines rather than the texture, and in no one point can the 
appearance of the bridge be more completely made or marred than 
in the treatment of the grade line. The optical effect resulting from 
different combinations is a matter warranting the most careful and 
painstaking study. The ancient Greeks and Komans, whose archi- 
tecture has withstood the criticism of 20 centuries, gave a prominence 
to this phase of design which has been more or less lost sight of in 
modern times. The broad, majestic, circular steps which add so 
much to the appearance of many of the ancient edifices, are in reality 
not flat and level tables, as they appear to be, but are warped at the 
ends just sufficiently to counteract the foreshortening of the per- 
spective and thus create the optical impression of a truly level plane. 
This is one of many examples illustrating the tendency in ancient 
architecture to take cognizance of optical illusions and artificially 
