4 BULLETIN 1486, IT. S. DEPARTMENT OF AGRICULTURE 
UNDESIRABLE FEATURES IN ALIGNMENT 
Location resulting in through cuts which are apt to drift full of snow in winter. 
Location along sidehills of shifting or sliding material or along seepy or wet 
sidehills. 
Location over swampy or seep} r material or over ground where natural drainage 
is difficult or uncertain. 
Location on sidehills having a north exposure. These are apt to be wet a 
greater portion of the time than sidehill cuts having the benefit of south exposure 
sunlight. 
Adverse grade. 
Sharp breaks in grade. 
Blind curves or restricted sight distance. 
Reverse curvature (on account of the difficulty of properly superelevating the 
roadway) . 
"Broken backs" or two curves in the same direction with a short connecting 
tangent. 
DESIRABLE FEATURES IN CULVERT LOCATION 
Adequate vertical clearance to eliminate possibility of culvert running under 
a head at flood periods. Culverts may be subjected to a considerable head 
without danger, but the likelihood of erosion at the lower end of barrel and also 
of damage to the fill adjacent, is such as to render this construction poor practice. 
Adequate vertical clearance for ice or drift. This in many cases requires a 
clearance several feet above extreme high water. 
Adequate horizontal clearances to avoid accumulation of drift or debris during 
freshets. Narrow openings on streams carrying gravel in suspension have been 
known to become completely clogged during freshets, thus causing a washout of 
the adjacent embankment. 
UNDESIRABLE FEATURES IN CULVERT LOCATION 
Skew crossings are not altogether objectionable but should be avoided where 
possible. 
Location over swampy or soft foundation material. 
Location below a sharp bend or kink in the general stream alignment. This is 
apt to cause erosion behind upstream wings or cutting of adjacent embankment. 
Location at point of rapid fall where erosion of footings at downstream end of 
structure is possible. 
Location such as may tend to divert the stream from its natural course during 
freshets with consequent damage to property, as illustrated at point C in Figure 1. 
COST CONSIDERATIONS INVOLVED IN THE LOCATION OF LARGE 
STRUCTURES 
For larger and more important construction, the matter of location 
for the bridge structure becomes increasingly important and tends 
more and more to outweigh considerations of cost as affecting the 
approach alignment. The following factors are among the many 
which should be considered in making a bridge location. 
LENGTH OF CROSSING 
Other things being equal, the location of a bridge structure should 
take advantage of any narrow neck or point of constriction in the 
waterway, due to steep, high banks. The two locations shown in 
Figure 2 illustrate the difference in cost which may accrue from this 
source. These are two crossings of the same river. Crossing No. 2 
is several miles down stream from crossing No. 1, yet involves con- 
siderably less material, owing to the fact that advantage was taken of 
a steep, rock gorge of comparatively narrow width. Both crossings 
are over exposed rock, but the natural banks at the site of crossing 
No. 2 lend themselves to a shorter channel span, the channel being 
deeper as well as narrower, thus affording greater waterway area for 
