A list of interchange types is found on Kurumi.com. I refer to them by name frequently on this site.
State initials followed by a number (e.g. AL 9) = numbered state highway or route, basically just omitting the term "Highway" or "Route." Some states use the first initial only, with a hyphen: Colorado, Michigan, Kansas, Utah. I use "SR" for Indiana because "IN 100" just looks weird.
Number followed by x's = a group of highways sharing one or more listed digits, with variations in the "x" digits. For example: 5xx encompasses 501 to 599.
2di, 3di = 2 or 3-digit interstate (2 digit interstate)
2dus, 3dus = 2 or 3-digit U.S. Route
AADT = Average Annual Daily Traffic. Traffic counts may be found at state DOT websites.
AASHTO = American Association of State Highway and Transportation Officials, originally AASHO (sets US and Interstate route numbering, among other duties)
A- = Autoroute, Autostrada, etc.
Alt. = Alternate
BGS = Big Green Sign, a creative name for highway and freeway guide signs over a certain size. Similarly, BBS for blue, brown, or black; BYS for yellow; etc.
BL/BS = Business Loop/Spur
Bus. = Business
Byp. = Bypass
C-D = Collector-Distributor, a roadway (set of lanes) paralleling one side of a highway or freeway used to separate multiple entrances and/or exits from the main freeway lanes. Unlike frontage roads, C-D roads are freeways or expressways without driveway access or cross traffic.
CAD = Computer-Aided Design, the use of computer programs to draft highway plans. "CADD" adds "Drafting" to the acronym.
CCW = Counterclockwise (see CW)
CMS = Changeable Message Sign (see VMS)
CR = County Route/Road
CTH = County Trunk Highway (Wisconsin)
CW = Clockwise (see CCW)
DOT/DOH = Department of Transportation/Highways
EB = Eastbound
ETC = Electronic Toll Collection
FAP/FAS = Federal Aid Primary/Secondary, a national classification system of important routes that qualify for Federal funding.
FHWA = Federal Highway Administration, which administers Federal highway spending.
HOT = High Occupancy Toll, an HOV lane that allows single-occupancy vehicles to use it for a fee.
HOV = High Occupancy Vehicle, a lane restricted to vehicles with a certain number of occupants (and sometimes motorcycles and/or hybrid cars).
I- = Interstate
ITS = Intelligent Transportation Systems, which consists of sensors, VMS, and other infrastructure that determines roadway conditions and transmits it to the public, news agencies, DOTs, etc. Often there is some human element capturing or processing the data before it is disseminated.
KH = King's Highway (Ontario)
LGS = Little Green Sign (see BGS)
LOS = Level of Service. This is a traffic engineering term and ranges from LOS A (free-flowing traffic) to LOS F (traffic crawling or completely stopped).
MP = Milepost
MPO = Metropolitan Planning Organization, a city- or regional-level group (unlike a state DOT) that sets goals for development to guide future projects.
MUTCD = Manual on Uniform Traffic Control Devices, published by the FHWA.
NB = Northbound (also NEB or NWB, rarely, for Northeast or Northwest)
NHS = National Highway System, a federally funded system of routes (see FAP/FAS).
NIMBY = Not In My Back Yard, a person who opposes a project because of its nearby location
NJSHR = See SR/SH.
ROW = Right of Way, which can either mean land considered highway property or the right to proceed through an intersection over other drivers. Typically the abbreviation is only used in the first context.
RR = Railroad (usually), Regional Road (in Ontario when followed by a route number)
SB = Southbound (also SEB or SWB, rarely, for Southeast or Southwest)
SH/SR = State Route/Road/Highway. Also see SR = Secondary Route. SHR is State Highway Route, used to refer to pre-1953 route numbers in NJ.
SLD = Straight Line Diagrams, which are gussied-up stick diagrams used by NJ and some other DOTs as a semi-official route log. It includes information such as cross streets, mileposts, concurrencies, speed limits, roadway widths, control sections, contract numbers, structure numbers... the list goes on.
SPUI = Single Point Urban Interchange, a configuration similar to a diamond except all left turns are made from a single point in the middle.
SR = Secondary Route. Alse see "SH/SR" for SR = State Route/Road. In certain states like West Virginia, Virginia, and Pennsylvania, instead of (or in addition to) having a county route system, the state maintains an extensive secondary system. There is always a distinction in signage between primary and secondary systems. Some states like Tennessee use a different shaped shield, some states like North Carolina use small marker signs that are not shields, and some states like Vermont do not provide any signage other than reference markers. Typically, SR is used for secondary route when there is an overlapping route numbering system, such as in Virginia when they repeat by county, and may not be used in a state like Tennessee where the secondary and primary route systems are numbered as one.
TCH = Trans-Canada Highway
Temp. = Temporary
TR = Town/Township Route/Road
Twp. = Township
VMS = Variable Message Sign, which can either be a rotating-drum type (see CMS) or light-matrix type. Rotating drum CMS can only display a few messages, while light-matrix (or similar) VMS can display any messages that fit on the sign.
WB = Westbound
A, B, C, D, E, F = Names of Highway Gothic font styles. A is the narrowest, F is the widest. Sometimes referred to as "Series." There's also an E Modified, which was used for button copy and is still used on highway signs.
Abutment = The large concrete or stone structure beneath either end of a bridge that "holds it up."
Alignment = The path of a route. Old or former alignments are paths that the route no longer follows, frequently converted into Business Routes or county routes, or else partially abandoned.
Assembly = A group of separate signs located next to each other that together function as a single sign. For example, "EAST" "46" "NEXT RIGHT" would typically be found on three separate signs, but the entire message is read as a unit.
At grade = A road that sits at ground ("grade") level. Usually used in reference to an intersection, where both roads meet at the same level instead of one crossing the other on an overpass.
Banner = A small sign, such as a directional banner (the "EAST" above a route marker, for example).
Bannered route = A route differentiated from the mainline by an added banner; note that some states may put the text of the banner directly in the route shield instead. Typical examples: Alternate, Business, Bypass, Connector, Spur, Truck.
Blank (noun) = A sign, typically a route shield, that is made to a generic pattern with specific text left off. For example, a US shield blank can be used for any US highway that fits inside. These are often used for construction because they can be reused on many projects.
Braided = Generally applied to ramps; braided ramps occur when two ramps run next to each other, one crosses over the other, and they continue to run next to each other, but there's no access between them. It's usually done when two interchanges are so close to each other that the onramp can't merge into the highway properly before the next exit would leave.
Bump = A situation where two roads or routes meet each other but do not cross or multiplex (i.e., one or both of them turns at the intersection or interchange).
Business Route = A loop or spur off a highway into the center of a town. Often a loop is an old alignment of the highway. See this list of Interstate business routes and this list of US Highway business and other routes.
Button Copy = Sign legends where reflectivity is achieved by inlaid glass or plastic reflectors in the sign. These are no longer used due to cost.
Carriageway = A single roadway, usually used in context of a dualized highway (which would have two carriageways).
Cat's Eyes = An early type of reflector similar to glass marbles used in sign legends.
Centerline = The yellow striped markings (in the USA) in the center of a roadway. If no marking is present, this may be the top of the roadway "crown" (the highest point in cross section) or the joint between concrete slabs.
Channelized = Striping or (more typically) a curbed island is used to separate traffic flows by direction. This term is usually used at an intersection, as interchange ramps are channelized by definition.
Child route = A route whose numbering (and sometimes very existence) is directly related to a route it connects to. This is common on the Interstate and US Highway systems (3-digit routes are "children" of the 2-digit "parents"). A child route can also be a lettered route (e.g., 4A and 4B are children of 4) or a bannered route.
Clearview = A new sign font being used on a trial basis by some states (Michigan, Pennsylvania) and state agencies (NY Thruway Authority). The standard font that has been used for decades is known as FHWA Gothic.
Clinch = Travel the entire length of a named or numbered highway. "Certified" is used by some to denote having clinched both directions. "Conquered" is also used to denote having traveled on some part of the highway.
Concurrency = Two or more route numbers on the same highway. This term is used interchangeably with "multiplex," and terms like duplex, triplex, quadruplex, quintuplex, etc. find their way into usage as well.
Control City = The destination(s) listed on a guide sign for a particular route.
Control Section = One section of a highway designated by the DOT. A single control section was probably built or upgraded in a single contract. Control section designations are usually not signed.
Copy = Sign lettering.
Cross traffic = Any situation where traffic from a side street may either turn across and/or continue across a highway. If there is a traffic signal or stop sign on the main highway, it would be considered to have cross traffic.
Decommissioned/Downloaded = A route that has been dropped from its former status (Interstate, US, state, county), or at least removed from its former route. "Downloaded" implies that another highway agency has picked up the route - for example, a former US highway may be downloaded to the state or county and still have a route number.
Diagrammatic = A sign that shows the upcoming road layout in arrow form. This is usually a large overhead green sign with a large white arrow and one or more smaller arrows branching off of it. These often show little black lane lines following the arrows to show the upcoming lane configuration as well.
Dualized = Having two roadways, one in each direction. Also known as a divided highway. Dualization (or twinning) is the act of converting a highway from a single roadway to a dualized roadway. Sometimes the old roadway becomes one of the two new roadways, and sometimes the two new roadways are on a new alignment.
Duplex = A multiplex of two routes. See Concurrency.
Expressway = A highway with cross traffic but no driveways ("limited access"). If there is no cross traffic, it is a Freeway even if the name is Expressway.
Field = "In the field" means "as seen in the real world."
Flyover = A roadway, usually a ramp, that passes above one or more other roadways. It's like an overpass, but tends to be higher and/or curved in shape. "Flyunder" is a variant.
Freeway = A highway with no cross traffic and no driveways ("controlled and limited access"). Some parts of the country call these Expressways. Some Parkways also fall under the Freeway definition.
Frontage road = Also known as a service road, this is a road on one or both sides of a freeway (occasionally expressway) that has cross traffic and driveways so that the mainline does not. These may be one-way or two-way.
Gantry = Also known as a "sign bridge," an overhead highway structure that holds or is intended to hold several signs, usually spanning an entire roadway.
Gore = The area between a roadway and a ramp as they separate or come together.
Grade separation = A road that is not at grade, usually used in reference to an intersection or interchange.
Greenout/Greened out = A patch that is applied to a BGS or LGS (or the process by which the patch is applied) to cover some part of the original legend on the shield. This may be done to correct errors, to change destinations or routes, or to cover over information that no longer applies. The same process may be applied to other color signs, but "brownout," "blueout," etc. are almost never used.
Highway = General term for a through road, usually one with a route number.
Interchange/Intersection = Interchanges involve grade separation, and interchanges are at grade.
Island = An area within a highway right-of-way not intended for travel, whether striped, curbed, a grassy expanse, etc. Islands may be anywhere, including in the median, channelizing a turning lane from through traffic, or even between same-direction traffic (such as at a toll plaza).
Jersey Barrier = The shape of concrete barrier commonly seen in highway medians now, originally tested and developed in New Jersey.
Jersey Freeway = A highway with no cross traffic but driveways ("controlled access"). Found more often in New Jersey than other states.
Jughandle = A type of at-grade intersection that involves ramps, usually found in New Jersey. The jughandle ramp either exits forward to a cross street or loops around and exits backward after the cross street. Some more complicated intersections with several jughandles mimic interchanges.
Lazy T = A variation on a T intersection where the road ends at the through street with angles that are not close to 90 degrees.
Legend = Letters, numbers, arrows, borders, etc. on a sign background, but excluding route shields. If you're on a highway and see a BGS (see Abbreviations), legend is everything that appears in white.
Mainline = The highway that is being traveled on or referred to. Often used to denote the main highway when referring to a frontage road, C-D road, Business Route, old alignment, etc.
Mast Arm = The horizontal part of an overhead traffic signal that projects out over the road from the pole.
Median = The center of a highway, typically only used when there is a barrier or grassy expanse separating the two sides.
Milepost = Technically the little sign (usually green or blue) noting distance from the beginning of the highway in the state, but may also be used to refer to a particular mile whether or not there is a post sign.
Motorway = Non-American English term for a freeway.
Multiplex = See Concurrency.
Parapet = All elements of the side of a bridge above the deck, usually consisting primarily of a barrier and/or decorative railing.
Parent route = See Child route.
Pony truss = A truss bridge (see Truss) where there is truss structure rising above the roadway surface on both sides, but not tall enough to have support beams crossing overhead. By contrast, see Through truss.
Pullthrough/Pull-through = An overhead sign for the through route (or a major diverging route) that tells you the destinations ahead.
Reference Marker = Small signs periodically placed at the edge of highways intended for use by DOTs only (state or county), either for maintenance reference or internal bookkeeping. In most states that post reference markers, the route number is included somewhere on the sign.
Right of Way = See "ROW" in abbreviations.
Road Enthusiast / Roadgeek = Those of us who attend road meets and enjoy highways as a hobby and/or pastime.
Road Meet = A planned event, announced to the general road enthusiast community, usually featuring lunch followed by an area tour encompassing new construction, abandoned highways, and other items of interest. There are occasional multi-day meets of a more national nature, and mini-meets that are less widely broadcast and of a smaller scope.
Series A, B, etc. - See "A, B, C, D, E, F."
Shield = Route marker, including the number and the shape.
Slip ramp = A high-speed, shallow angle ramp connecting two parallel, same direction roadways. This is commonly seen when a ramp leaves the left side of a frontage road and joins the right side of the freeway.
Stack = An interchange where all movements are fully directional (there is no weaving). A classic East Coast stack is I-90/US 9 north of Albany, NY. If you look at an aerial photo of it, you'll know what a typical stack is.
Suicide lane = A central lane on a three-lane roadway that allows passing by either direction of traffic. The original suicide lanes did not provide any preference for passing direction, either by having dashed yellow stripes on both sides or having no stripes at all (such as Colonial Parkway in Virginia). Modern suicide lanes, which are much safer, provide a preference by striping one direction as having two lanes and allowing the other side to pass with a permissively striped centerline.
Super 2 = A freeway with one lane in either direction, usually without a center median barrier. Super 3 is a variant where there are passing lanes on either side, although those may be lumped in with Super 2 with no distinction.
T intersection = An intersection where one road ends at another, with an approximate 90 degree angle between. See Lazy T.
Through truss = A truss bridge (see Truss) where cars are surrounded by the truss structure on both sides and on top. If there are support beams crossing the road overhead, it's a through truss. Also see Pony truss.
Triplex = A multiplex of three routes. See Concurrency.
Truss = A bridge type made up of several connecting members, usually made of steel. Trusses may be under the deck, above the deck, or both. There are many types of trusses, some of which are more specific than others. I define the more general ones here - see Pony truss and Through truss.
Twinned = See Dualized.
Unisign = What would normally be multiple signs (e.g., "North" "US 1" "Next Right"), combined on a single sign panel, with the appearance of being separate signs.
Upgraded/Uploaded = An existing road receiving a route number or being elevated to a higher type of route. Upgraded routes undergo construction to dualize or otherwise improve the road, while uploaded routes may just be incorporated as they are.
Weaving = Traffic streams crossing along a short length of roadway, best illustrated by an example. You are on Roadway A. There's an entrance into Roadway A where vehicles are coming on. A short distance later, there's an exit from Roadway A where vehicles are leaving. If the entrance and exit are on the same side, the vehicles coming onto Roadway A end up crossing paths with the vehicles leaving Roadway A. If the entrance and exit are on opposite sides, the vehicles coming onto Roadway A who want to leave at the next exit have to cross paths with everyone else on Roadway A. The shorter the distance between the entrance and exit, the less time there is for the paths to cross and the worse the traffic conditions, which is known as a more "intense" weave.
Wye/Y intersection = An intersection that would look like a Y if viewed from the air. This can be a variation on a T intersection where the ending road splits in two forks, or it can have all three roads coming in and splitting in a triangle.
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