of Road & Traffic Terms
|This page last updated May 23, 2021
is a list of common highway-related words and terms, both the technical
jargon as well as layman's terms, and their definitions, especially as
they apply here in Texas.
lane - a short lane at the end of an entrance ramp that
allows entering traffic to build-up speed before merging into the main
travel lanes. In San Antonio, and in Texas in general, acceleration
lanes are not as common as in other states.
road - the common term in San Antonio for a frontage
- a main road or thoroughfare. Arterials are typically
divided into "major arterials" and "minor arterials".
lane - a lane that is added to a freeway at an entrance ramp
and then is subsequently dropped at a downstream (usually the next)
exit ramp. Compare with acceleration
lane, deceleration lane, mainlanes, and
annual daily traffic (AADT) - a traffic count that counts
the number of vehicles that pass a given point on a road during a
24-hour period, averaged over several counts taken during a 12 month
Dance - a colloquial term for a pedestrian scramble.
- technical term for a bridge column.
Dots - colloquial term for raised pavement markers,
also known as "traffic buttons" and "turtles". Named for the traffic
engineer who invented them.
ramp - a ramp configuration where an entrance ramp
passes over an exit ramp, or vice-versa. Braided ramps eliminate
areas with limited room for conventional slip ramps. See also slip
eyes - colloquial term for reflectorized raised
mile - technical term for one mile of a roadway, regardless
of the number of lanes. Compare with lane mile.
message sign (CMS) - another term for a variable
- the area adjacent to a roadway that, by design, is kept
clear of immovable objects for safety reasons.
- an interchange that has four circular ramps that turn at
270 degrees to provide for left turn movements (which, when viewed from
above, resembles a four-leaf clover) and four outer 45-degree ramps for
right-turn movements. Many people refer to any freeway-to-freeway
interchange as a "cloverleaf", but the term should only be used for the
specific type of interchange with circular ramps. Compare with directional
- a street that provides connectivity between an arterial
and local streets. The main street into and through a subdivision is
typically a collector.
roadway that runs parallel to but is separate from the freeway
mainlanes and from the frontage road and provides
connectivity between the mainlanes and
another roadway. These are often used in interchanges where traffic
exits the freeway onto the collector/distributor, then exits again from
the collector/distributor onto an exit ramp. Some people mistakenly
conflate collector/distributors and frontage roads.
rail - a type of public rail transportation that connects a
central city with its outlying suburbs, satellite towns, or another
city. Many people interchange the terms "commuter rail" and "light
rail", but this is incorrect. Commuter rail differs from light rail in
that is uses larger, heavier trains (such as subway or Amtrak style
trains) that run entirely on exclusive rights-of-way. Commuter rail
also specifically differs from light rail in that it connects a central
city with its outlying areas and has far fewer stations and
less-frequent schedules (headways) than a typical light rail system.
See also light rail.
- when a single physical roadway shares two or more route
numbers, for example, if a single road is both I-10 and US 87.
- a ramp, often elevated, that connects two highways. These
are commonly just referred to as a "ramp" or, if elevated, a "flyover".
- a type of roadway whereby traffic can only enter and exit
at specific designated locations (i.e. entrance and exit ramps.)
Controlled access roads are generally referred to as freeways or
- a paved area in a median of a divided highway where
traffic is allowed to cross over to the other side of the highway or to
an intersecting road. Compare with turnaround.
lane - a short lane just prior to an exit ramp that allows
exiting traffic to reduce speed before leaving the main travel lanes.
In Texas in general, deceleration lanes are not as
common as in other states.
interchange - an
interchange between a freeway and surface street where the entrance and
exit ramps form a diamond shape as viewed from above. In most places
outside of Texas,
the ramps connect directly from the freeway to the surface street, and
so the diamond pattern is obvious. In Texas, however, the ramps usually
connect to a frontage road, so the diamond may be elongated.
In congested areas with
frontage roads, diamond interchanges are oftentimes replaced with
X-interchanges to reduce weaving on the mainlanes. Compare with
interchange - an interchange, usually a freeway-to-freeway
interchange, where connectors, typically elevated ("flyovers"), provide
direct connections to the intersecting roadway by turning in the
direction of travel. In other words, the connector for the left turn
movement actually bends to the left rather than making a 270-degree
right turn as it does in a cloverleaf interchange. Most
fully-directional interchanges are known colloquially as "stacks" or
Compare with cloverleaf.
displaced left turn (DLT) - an
intersection where one or both left turn movements of one or both
intersecting roadways is shifted to cross over the opposing traffic
lanes prior to reaching the main intersection. This allows two or more
normally conflicting movements to travel simultaneously, thus
increasing the efficiency and capacity of the intersection. Also known as a "Continuous Flow Intersection".
diverging diamond interchange (DDI) - an
intersection-- typically where an arterial crosses a freeway-- where
the opposing traffic on the arterial crosses over to the left side
while traversing the interchange, then crosses back to the right side.
This allows for left turns to be made without crossing opposing traffic
and for two or more
normally conflicting movements to travel simultaneously, thus
increasing the efficiency and capacity of the intersection.
highway - a roadway that has a median or some other physical
barrier separating the two opposing sides of traffic. Some people
automatically assume that any divided highway is a freeway or
expressway, but this is an incorrect assumption. While nearly all
freeways are divided highways, not all divided highways are freeways.
message sign (DMS) - another term for a variable
- the use of a part of private property for a public
purpose. Typically, easements are used for utility lines. Owners of
property with an easement are required to provide access to the
easement and are typically not compensated for the use. Compare with right-of-way.
- a road that has controlled-access. In most parts of the
country, including Texas, the term "expressway" and "freeway" are
essentially interchangeable. However, the technical term "expressway"
differs from "freeway" in that expressways can have at-grade
intersections, whereas freeways cannot. Compare with freeway,
highway, and parkway.
(FM) road - the network of rural roads in Texas that connect
farming and ranching areas with nearby towns. The FM system also
contains Ranch-to-Market (RM) roads. In metropolitan areas, many FM
roads no longer serve that purpose and instead are simply
road - the common term in Houston and southeast Texas for a frontage
- a colloquial term for an overpass, especially an overpass
that is an interchange ramp or connector.
- a road designed for high-speed traffic with
controlled-access and grade-separated intersections. Contrary to
popular belief, a freeway is not necessarily a road free from tolls,
but rather a
road that is free from signals and intersections; a "free-flowing"
road. Indeed, when one uses the term freeway, it conjures images of a
certain type of road based on its functional capabilities, and, in
fact, most tollways are functionally-classified as freeways. Compare to
expressway, highway, and parkway.
road - a
road that runs parallel to a freeway or expressway for the purpose of
providing access to adjacent properties and intersecting surface
streets. Typically, there will be a frontage road on each side of
a freeway. In urban areas, frontage roads are one-way, while they
are usually two-way in rural areas. While they are referred to
colloquially as access
roads in San Antonio, feeder
roads in Houston,
El Paso, and service
roads in Dallas, "frontage road" is
the official term and is also the common term in the Austin area.
- the common term in El Paso for a frontage road.
- an intersection of two roads where one roadway passes over
the other. In other words, the roads do not intersect at-grade. Every
intersection along a freeway is grade-separated. See also interchange.
heavy rail - a type of public rail transportation/rapid transit that utilizes subway-type trains running in a dedicated
exclusive right-of-way. Compare with light rail and commuter
Occupancy Toll (HOT) lane - a dedicated lane that
can be used for free by vehicles that have a minimum number of
occupants, typically 2 or more, and can also be used for a fee (toll)
by single-occupant vehicles.
Occupancy Vehicle (HOV) lane - a dedicated lane for vehicles
that have a minimum number of occupants, typically 2 or more. HOV lanes
are used extensively in the Houston area and are also found in the
Dallas and San Antonio areas. Many HOV lanes in Texas and elsewhere
have been converted to HOT
lanes or tolled managed
- as defined by law,
a highway is any public roadway. Typically, the term "highway" is
generally used to refer to a major roadway, usually maintained by the
state. In many places, the term is often used colloquially to
refer to a freeway.
Transportation System (ITS) - a system that uses various
to monitor and manage traffic on a roadway or network of roadways such
as TransGuide in San Antonio and TransStar
grade-separated junction of two roadways with full or partial access
between them. Technically, the term "interchange" can refer to a
junction between a freeway and a surface street, but often the term
is primarily used to refer to freeway-to-freeway intersections.
sequence series sign - a road sign that lists the next
three (sometimes two) exits and the distance to each. Interchange
sequence series signs are typically used in urban areas.
- a system whereby traffic signals communicate with each
other and/or a central controller, usually as part of a coordinated
progression system. This can be done by means of a
cable, dedicated radio, or cellular
modems. See also progression.
- a freeway that is part of the federally-designated
Interstate Highway System. This term is often used colloquially
(although technically incorrectly) to refer to any freeway.
barrier - the
ubiquitous concrete barrier used to separate opposing traffic flows on
freeways as well as protective barriers in construction zones and as
bridge rails. The term "Jersey barrier" technically refers to a
specific type of barrier, but is commonly used to refer to all sloped
concrete barriers. Newer concrete barriers that are not technically
"Jersey barriers" are generally "constant slope" barriers. Jersey
barriers are known as "K-rails" in some areas.
control signal (LCS) - a
signal above a lane that shows a red, green, or yellow arrow or "X"
symbol to denote whether the lane is open or closed.
drop - a place on a freeway or other roadway where a lane terminates by
either becoming an an exit-only lane or by way of simply ending and
merging into the adjacent lane. Also see trap lane.
mile - one mile of one lane of road. One mile of a roadway
with four lanes is four lane miles. Contrast with centerline
of service (LOS) - a mostly subjective measurement of the
performance of a roadway or intersection based on the traffic
conditions. LOS is graded on a scale of A-F (including E), where LOS-A
is free-flowing traffic and LOS-F is heavy stop-and-go congestion.
rail - a type of public rail transportation that utilizes
streetcar-like vehicles either on streets with shared right-of-way
exclusive right-of-way. The term "light tail" is sometimes incorrectly
used interchangeably with "commuter rail". Compare with commuter
rail and heavy rail.
- another term for controlled access.
Texas, a loop is a state highway that connects two or more other state
highways. Usually, a loop is circular in nature, but frequently is
not. Perhaps the best-known non-circular "loop" in Texas is
1, or MoPac Expressway, in Austin.
- the main or primary travel lanes or through lanes on a freeway or other
highway, as opposed to the frontage road lanes. See also acceleration
lane, deceleration lane, auxiliary lane, and
thoroughfare plan - a plan by a municipality, county, or
other transportation planning agency that classifies existing arterial
roadways and designates corridors for possible future arterials. The
primary purpose of such a plan is twofold-- to designate roadways for
funding purposes, and to lay out a comprehensive road network so as to
preserve the locations for possible future roads.
lane - a lane or set of lanes on a road, typically on a
freeway, that are separated from the general-purpose mainlanes by
barriers, to which access is regulated by some criteria
(for example payment of a toll, occupancy requirements, or vehicle
type) to maintain a desired level
of Uniform Traffic Control Devices (MUTCD) - the
guide that defines and regulates all traffic signs, signals, and
markings in the United States. Some states adopt the federal MUTCD
directly with or without an addendum, while other states have their own
MUTCD based on the federal version.
- an unpaved area that separates two parallel roadways.
Sometimes mispronounced or misspelled as "medium".
Planning Organization (MPO) - a state-designated agency that
is required under federal law to coordinate federal and state
transportation funding among all agencies that receive such funding in
a metropolitan area.
mill and overlay - See overlay.
- another term for
overlay - TxDOT-speak
for resurfacing a roadway, i.e. new asphalt is overlaid on the old
surface, which has typically been "milled" (ground down) first.
- a roadway that typically runs through a park-like setting.
In the Northeast, parkways are generally freeways where commercial
vehicles are prohibited. In Texas and many other places, the term is used
somewhat arbitrarily on roads that might otherwise be called a
boulevard or avenue. In San Antonio, the term "parkway" has also been
used in another context, that being a roadway that is
essentially a minor expressway or "super-arterial", namely the
scramble - an intersection where signals stop all motor
traffic to allow pedestrians to cross in all directions simultaneously.
Also known as a "Barnes Dance" (named for the traffic engineer who
reportedly invented it.)
system whereby specific vehicles can interrupt the normal traffic
signal cycle to gain priority. In many cities, signal pre-emption is
used by emergency vehicles. Some public transit buses also have
capabilities along some or all of their routes. Railroads crossings
near signalized intersections also have pre-emption capabilties; in
those cases, pre-emption usually takes the form of sending the traffic
signals into flash mode while a train is present, followed by a special
sequence to help clear traffic after the train has passed.
- a system whereby traffic signals are coordinated along a
given corridor to provide for all green signals as a group of vehicles
(known as a "platoon") makes its way through the corridor at a set
speed. Known colloquially as "synchronization". See also
pavement marker - a
device, usually made of ceramic or plastic, that is used as a lane
marker. These are known colloquially as "Botts' Dots", "turtles", or
"traffic buttons". Oftentimes, raised pavement markers will be
reflectorized; these are sometimes known as "cat's eyes".
- a short road that provides a connection between two other
roads. See also slip-ramp and connector.
metering - a
system that uses traffic signals on a freeway entrance ramp to regulate
(meter) the number of vehicles that can enter the freeway, typically
during peak periods. Houston, Dallas, San Antonio, and Austin all had
ramp metering in the '60s, '70s, and '80s that was removed in
subsequent expansions. Ramp metering, branded as "flow signals", was
reintroduced in Houston in the mid '90s, although many have again been
subsequently removed during expansion projects.
Road - another term for a Ranch-to-Market road, although
there is one official "Ranch Road" (RR1) that serves the LBJ Ranch. See
road - another name for a Farm-to-Market road.
The term "Ranch-to-Market" is more often
used west of US 281.
- 1. a strip of land owned by a public entity for use by
transportation, utility, and/or communication purposes. Compare with easement.
2. the legal authority of one vehicle to have priority over another
at an intersection.
- pavement or other treatment along a slope or around a post
or column to prevent
- a roadway intersection that utilizes a circular roadway to
connect the intersecting roads. Roundabouts, sometimes incorrectly
referred to as "traffic circles" (which are larger), are a form of traffic
road - the common term in Dallas-Ft. Worth for a frontage
- a paved area adjacent to a travel lane, typically on the
right-hand edge of the road, that is not intended for use as a main
travel lane, but rather as an area for vehicles to slow or stop in an
emergency or to turn right. In Texas, an improved shoulder (one that is
paved and of similar width to a normal travel lane) can also be used to
pass someone who is slowing or stopped to turn left on the main travel
lane or can be driven on by slow vehicles to allow faster traffic to
pre-emption - See pre-emption.
single point urban interchange (SPUI) - a type of diamond
interchange whereby the left turn movements are curved in
such as way
as to provide a single intersection for them centered under or above
the freeway instead of two distinct intersections on each side of the
freeway. The first SPUI in Texas was at US 75 and Parker Rd. in Plano.
ramp - a short ramp between two adjacent, parallel roads,
such as the entrance and exit ramps between a freeway's mainlanes and
bowl - a colloquial term for a stack interchange.
- a short state highway that branches-off from another
- a multi-level, fully-directional interchange between two
freeways, so-called because the roadways and flyovers are "stacked" one
atop the other. Also see directional
highway - 1. any roadway built and maintained by the state.
2. in Texas, a specific class of roadway-- typically a trunk road-- that is part
of the state highway
system and are marked with a black and white square sign with the route
number and the word "Texas". These route numbers are prefixed with "SH"
in TxDOT nomenclature.
- a roadway with one
or more intersections where the straight-through and left-turn
movements of the cross street have been eliminated and replaced by
right-turns coupled with downstream turnarounds. The first superstreet
in Texas was built on US 281 north of Loop 1604 in San Antonio, but has since been replaced by a freeway.
Superstreets are sometimes incorrectly called "Michigan Lefts", which
are similar but have a different traffic pattern.
street - a standard road that runs at ground level. This
term is generally used to differentiate a particular road from a
- a road where motorists are charged a fee to use the road.
Because of the inherent need to control access to a tollway for the
purposes of toll collection, nearly all tollways are also freeways.
Sometimes, tollways are built as managed lanes on an otherwise
toll-free freeway. See also freeway.
button - colloquial
term for raised pavement markers, also known as
"Bott's dots" and "turtles".
calming - techniques used to slow traffic. Such techniques
include roundabouts, speed humps, chicanes, and bottlenecking. See also
trap lane - A lane that terminates in a forced turn or exit (i.e. a turn-only or exit-only lane.) See also lane drop.
- a ramp that allows traffic to make a U-turn across a
divided highway. In Texas, turnarounds are used predominately to allow
traffic to go from a one-way frontage road on one side of a freeway to
the opposing one-way frontage road on the other side of the freeway
without having to traverse the intersections for the cross
term for raised pavement markers, also known as
"traffic buttons" and "Botts' Dots".
highway - a
highway that is part of the nationally-coordinated system of highways
that bear the same name. Contrary to popular belief, US highways
are not under any federal jurisdiction, but rather are state
highways that use a coordinated national numbering system to provide
for easier interstate travel. The numbering system is administered by
the American Association of State highway and Transportation Officials
message sign (VMS) - electronic signs along or above
freeways and other highways that provide dynamic messages to alert the
motoring public of incidents, congestion, construction, or other
information. VMSs are also known as "changeable message signs" and
miles traveled (VMT) - the
total number of miles driven by all vehicles on a specific road, class
of roads, or in a geographical area during a specific time period. For
instance, the total number of miles driven by all vehicles in Texas
during a specific year.
interchange between a freeway and a surface street where the entrance
and exit ramps connect to a frontage road and form an "X" shape
relative to the cross street as viewed from above. In a standard
frontage-road "diamond" interchange, the entrance ramp from one cross
street typically precedes the exit ramp for the next cross street.
However, in an X-ramp configuration, those ramps are reversed. This
reduces weaving on the mainlanes. The process of converting a diamond
interchange to an X-interchange is known as "ramp reversal". Compare
with diamond interchange.