HIGHWAY BRIDGE LOCATION 27 
Objectives for through routing. 
Service to pleasure resorts. 
Capitalization of natural scenic beauty spots. 
Service to natural through traffic trading points. 
Mileage considerations. 
Selection of the shortest possible routing for through traffic consist- 
ent with maximum service, as above outlined. 
REGIONAL TRAFFIC CONSIDERATIONS 
Industrial traffic service will be the most efficient where centers 
of production of raw material are connected by direct routing with 
their natural points of distribution, and where the centers of industry 
(mills, factories, etc.) are connected directly with the local supply of 
raw material. 
Pleasure traffic will be best served by direct connection of urban 
centers with natural pleasure resorts (taking into consideration, of 
course, the trend of future development). 
LOCAL TRAFFIC CONSIDERATIONS 
Maximum service to local traffic is obtained where traffic conges- 
tion is reduced to a minimum. Under this head falls the consideration 
of traffic loops, distribution plazas, etc. The question of traffic 
distribution at bridge terminals will be discussed in more detail else- 
where. However, in selecting the location of any bridge structure 
contiguous to an urban center, provision for such distribution and 
collection facilities, either present or future, should receive consider- 
ation. As illustrative of the foregoing, consider the plan shown in 
Figure 25, which shows a bridge crossing adjacent to a natural 
municipal traffic loop. For traffic originating or terminating within 
the loop, location C will best serve. This is also the most desirable 
location for traffic surrounding the loop if of equal density on all 
sides. If, on the other hand, a main trunk road is located as shown 
at F, the bridge may well be placed at location A to route through 
traffic out of the congestion at the loop. It may even be necessary 
to construct a ramp or diagonal graded approach at D to separate 
traffic quickly at the bridge head. If a large volume of traffic desir- 
ing to cross the stream enters the loop from the south at point E, 
then location B might receive consideration. 
In this discussion no attempt has been made to discuss and list 
all of the traffic problems involved in the selection of a bridge site 
nor to attempt to suggest a definite solution as this is a matter which 
can only be worked out for each individual case on its own merits. 
LOCATION OVER NAVIGABLE WATERS 
Perhaps the first and most important question to decide in locations 
over navigable waters is the choice between a high level structure and 
a structure provided with a movable channel span or spans. Again 
the basic principle of maximum traffic service at minimum cost may 
be stated as the controlling principle, but in this case service to 
water traffic as well as land traffic must be considered. Water trans- 
portation is best served by a high-level structure giving a vertical 
clearance sufficient to permit the passage of such water craft, present 
and future, as may operate over the waterway considered. High- 
masted schooner traffic will require a vertical clearance of 140 to 
