on the route recon overlay.
When the formula indicates an obstruction is
present, it must be marked on the recon overlay. In some cases, it may be
necessary to illustrate the obstruction with a sketch. Certain obstructions
must always be reported. These are as follows:
Overhead obstructions with a clearance of less than 4.3 meters
(14 feet). When a clearance is greater than 4.3 meters, it is
not considered an obstruction. For example, if there were an
overpass with a clearance of 5 meters, it would be listed in
the formula, but not listed as an obstruction.
Places where the road width is below standard for the type of
traffic flow. Road width dimensions will be discussed later.
These types of constriction are usually found at tunnels,
craters or rubble, or lanes through minefields.
Gradients (slopes) of 7 percent or more.
In other words,
Curves that have a radius of 25 meters (82.5 feet) or less.
In simple terms, if you extend the curve around to make a
circle, the radius of that circle must be more than 25 meters
or it is considered a sharp curve and an obstruction.
Any ferry or ford.
The effects of snow are not normally
considered an obstruction to traffic flow in route classification. This is
because of the variables such as snow depth and the availability of snow
removal equipment that are involved. When snow blockage is regular, happens
repeatedly, and is serious, it is noted by adding the symbol (T) at the end
of the formula. An example of such a situation would be the Donner Pass.
Floods are treated in the same manner as snow.
They are noted
only if they happen regularly and are serious. When that condition exists,
it is indicated by adding the symbol (W) at the end of the formula. Such
conditions might be anticipated along tidal rivers, for example.
Route Classification Formula Examples.
A great deal about a route can be told from the route
classification formula. It provides a summary of the route's limitations.
Here are a few examples with explanations to assist you in putting the
previous information together. It might be helpful to attempt to decipher
them before reading the explanation.
Then read the explanation and check
This formula describes a fair weather route (Z). The
minimum traveled way is 20 feet. It has a military load classification of