Transportation Structures:
Route Elements (Typologies Part 3)
and Glossary

Terms, Definitions and Observations

No, these aren't runes...

Over to "Transportation Structures - Route Typologies Part 1: Introduction and Outline of Lists"

Over to "Transportation Structures - Route Typologies Part 2: Descriptive Lists"

Listed in alphabetical order.

Route Elements

A "Route Element" is small, elemental feature in a route that is a transition or adjustment to a different type of route. They are usually a quick, sudden reaction to the terrain or an alteration in the route (which also makes them distinctive, recognizable and classifiable).
These are elements of a route independent of the terrain - only a two-dimensional view. For a three-dimensional perspective, see Route Subtypes or pathways

Since routes go both directions, it is arbitrary to choose between begin/end, past/before a crossing

Illustrations are scematic diagrams of each element. different routes are denoted by different colors.

[To combine with Glossary? Nomenclature?]

Route Elements: Topical List

Nominal

[Tangent]

Curves

Meetings

Route Elements: Entries

Bend

A kind of curve that is a sudden, abrupt change in route from one tangent to another - one bend with a change of the direction of the route.

Bend vs. dogleg - A dogleg is two bends with no change of the direction of the route. The Bend has one bend with a change of the direction of the route.

Same as Jog.

Often a result of shift of a road from one historic route to another.
Also conforming to survey lines (e.g. Virginia Millitary District), later ossified as property lines.
Also a result of inviolable property borders.
Also in section-line gridded roads, resulting from skew-corners of sections and others.
Most noticeable on level terrain, and thus with little logical explanation in regards to terrain (it usually is a result of illogical property lines).

Branch

One route begins on another route and heads off on a different course.

Branch vs. wye - A wye is two routes splitting off from a common point, both routes heading off on diffent courses. A branch is one route begining on another route and heading off on a different course.

Branch vs. crossing - A crossing is two entire routes crossing each other and retaining their general courses. A branch can be considered to have been two routes crossing each other, but half of the second route has been abandoned, leaving the other half to appear to start on the one route.

[need illus. of abandoned segment feeding in] Usually a result of part of one route being abandoned or obliterated past/before the crossing, leaving the other route to rely on the surviving route to take up its traffic.

Webster:

Crossing

Two routes cross each other and retain their general courses

Same as Node.

May also be referred to as a Node.
If one segment is abandoned, this becomes a branch.

Webster:

Dogleg

A kind of curve that is a Bend that bends suddenly, at a right angle or near-right angle, and then bends back again to parallel its original course, creating a Z or fortissimo or sharp music notation (for lack of better pictographs).

Two Bends or jogs close to each other that create a slight shift in the direction of the route, but not a change in its course.

Bend vs. Sway vs. Dogleg - A Bend is one bend with a change of the heading of the route. A sway is three bends with no change of the heading of the route; or, two doglegs that cancel each other out. The dogleg has two bends with no change of the heading of the route; or, two bends that cancel each other out.

Sometime a result of a gulley route as a transition between landforms.
Usually a small terrain element to retain the general route - a short bypass for the sake of efficiency.
Also, especially on trails and paths, originally resulting from a fallen tree or other obstacle that needed bypassing by has since disappeared. e.g. Buffalo Trail near Jackson - Mike Stroth.

Webster: (Dogleg) Noun: 1) A route, way or course that turns at a sharp angle.. Verb: To proceed around a sharp angle or along an angular or zigzig course. 1885-1890. (Doglegged) Adjective: Bent like the hind leg of a dog; zigzag. 1695-1705.

Jog

[should = sway! or too confusing - too broad a common term to use for technical definitions...] See bend: A kind of curve that is a sudden, abrupt change in route from one tangent to another - one bend with a change of the direction of the route. "A bend in the road."

Webster: Noun: 1) An irregularity of line or surface; projection, notch. 2) A bend or turn. Verb: To bend or turn. 1705-1715; variant of "jag."

Nexus

A node with more than two beginning/ending routes or more than one crosssing route.

Node

See Crossing: Two routes cross each other and retain their general courses.

Split

See Wye: Two routes splitting off from a common point, both routes heading off on a diffent course than the route they sprout from.

Webster:

Sway

A kind of curve that is a dogleg that returns to its original course and heading; or, two doglegs that cancel each other out.

Sway vs. dogleg and Bend: A sway has three bends with no permanent change in the course and direction of the route. A dogleg has two bends with a change in the course of the route, but no change of the direction of the route. A Bend has one bend with a change of both the course and direction of the route.

May also be called a "dodge" since the route is horizontally "dodging" something.
Usually a result of a waterway or terrain obstacle that is too minor to change the course of the route for, and that can be avoided by a quick side-stepping.
Sometimes called a jog - which may necessitate a revision of my nomenclature.

Webster: Sway: Noun or verb: 1) To move or swing to and fro. 2) To move or incline to one side or in a perticular direction. Swayback: Excessive downward curvature in the spine of animals (1865-70 American).

Switchback

The route abrubtly reverses direction, with no choice but for a vehicle to also reverse direction not by turning around, but by going into reverse (and then alternating forward and reverse).

Necessary only with auto vehicles (and probably impossible with horse-drawn vehicles).
Technically a kind of curve - an extreme curve
Theoretically two tight sways close to each other

Webster:

[Tangent]

A normal segment of a route: a stright stretch that is consistently on the course and heading.

or chord?...

Webster:

Wye

Two routes splitting off from a common point, both routes heading off on a different course than the route they sprout from. Named after the letter "Y" which illustrates the concept elegantly.

Wye vs. branch - A branch is one route begining on another route and heading off on a different course. The wye is two routes splitting off from a common point, both routes heading off on diffent courses.

Same as Split.

Less common than branch.
May be difficult to differentiate from a branch - the change in course may be subtle, or relative to the scale of analysis (the course to the next landmark, next crossing, next destination, next region?...).
May also be referred to as a split of feed-in.
A true convergence or divergence wye usually happens in the outskirts of important places - a result of the centripedal constriction of converging routes (e.g. Jackson). (Typically, whether the route convergence/divergence or the place came first is up for debate.)
Common term in railroad lingo: Since railroad tracks are by necessity linear and tangential, with different tracks in the same line merging smoothly into another at a switch, all their junctions are wyes.

Webster:

Typical location at shallow stream bed that maintains a stable location.
Usually created at confluences, islands (e.g. Ross 207 Infirmary Ford?), rapids (e.g. Natchez Trace), straight stretches (e.g. former US 50 at Dills, Reeves).

Webster: