misc.transport.road Frequently Asked Questions

3 Common Road and Highway Terms

3.1 Breezewood

This term refers to a stretch of surface road that connects two different freeways, or two different stretches of a single one, without any direct connection via an interchange. Usually, these roads are filled with traffic lights, gas stations, fast food joints, etc. The original example is in Breezewood, Pennsylvania, where I-70 follows surface US 30 for a quarter mile where it meets the Pennsylvania Turnpike. See http://www.fhwa.dot.gov/infrastructure/tollroad.htm or http://www.pahighways.com/interstates/I70.html for more details. Breezewood is the subject of a 2002 documentary by Jason Hutt called Breezewood, Pennsylvania (see 12.4.1 ). Oct 3, 2004

3.2 Business Routes

A loop or spur off a highway into the center of a town. Business routes generally have the same number of the main highway, but have special "Business" signs. Interstate business routes, for example, have special green shields, sometimes offset from the rest of a BGS by what MI's DOT calls an "accent square" (see http://mutcd.fhwa.dot.gov/HTM/2003r1/part2/part2d1.htm#section2D11 ). Most interstate business routes are surface streets, usually old alignments of US highways. Some are freeways, like the I-80 business loop in Sacramento (see http://www.cahighways.org/049-056.html#051 and http://www.interstate-guide.com/business-routes/bus80.html for details on and history of that particular route), but don't meet more technical interstate standards like ramp spacing. Sometimes but not often Interstate business routes are referred to as "green Interstates" in certain areas. The only Interstate business routes from the same parent to meet each other are I-44 BS and I-44 BL in MO ( http://www.cosmos-monitor.com/road/sign/mo/routeindex.html#BS44 ). US and state business routes are often the original route through the city. A list of Interstate business routes is at http://www.interstate-guide.com/business-routes/ and a list of U.S. business and other auxiliary routes is at http://www.us-highways.com/usban.htm . Jul 18, 2006

3.3 Button Copy

Button copy is a term used to describe letters and characters on signs with several inlaid reflectors in them, providing better visibility at night. States started phasing them out on signs at the end of the 20th Century, opting for reflective sign sheeting for the whole sign instead. See http://groups.google.com/group/misc.transport.road/msg/3d4e957b8741f740 (Message-ID: 3A3D4D1F.58FD0D6C@earthlink.net ). Jun 27, 2005

3.4 Control City

Usually associated with the Interstate Highway system, a control city is usually identified as the city on a sign which drivers are most likely to be headed. They appear as the bottom city on distance signs, on "pull-through" BGSes, and in signs leading to the freeway at interchanges. A complete list of control cities that AASHTO recommends for the Interstate system, as well as a more complete description, can be found at http://home.roadrunner.com/~pwolf/controlcities.html .

The cities on the exit signs on freeways are often called control cities as well on the newsgroup, as are the signs that say "City A ->" at an intersection, though these are officially known as "destinations". MUTCD sections: http://mutcd.fhwa.dot.gov/HTM/2003r1/part2/part2e1.htm#section2E12 (freeway/expressway), http://mutcd.fhwa.dot.gov/HTM/2003r1/part2/part2d2.htm#section2D34 (surface road) Oct 4, 2007

3.4.1

A:The longest distance on a conventional mileage sign, and one of only three four-digit instances, is probably 1007 miles for Los Angeles on I-40 in NM. Others of note are 1508 km (937 mi) for Yellowknife, NT ( http://albertaroads.homestead.com/transcanada/hwy16/hwy16w1.html - the largest number on a conventional distance sign), 857 (mi) for El Paso on I-10 in TX, and 1065 km (662 mi) for Fairbanks, AK on the Alaska Highway in YT ( http://www.teresco.org/pics/signs/20010613/84km-close.jpg ). Other very-long-distance controls include New York City in Ohio ( http://www.roadfan.com/nycohio.html ), on the New York State Thruway just into NY State, in Baltimore, and in Boston; Miami in VA; Tampa on I-285 in Atlanta; Memphis in Chicago; Tulsa in St. Louis; Los Angeles in the San Francisco Bay area; Manteo, NC on US 64 at the other end of NC; Denver in eastern KS; and various large western U.S. cities from other large western U.S. cities which contain no cities of note between them.

For non-conventional control cities, there are signs at highway termini which list distances to the other terminus. These include US 41's north end ( http://www-personal.umich.edu/~aleskiw/roadgeek/Gallery1.htm and http://www.geocities.com/usend4049/End041/end041.htm ) and I-70's east end ( http://www.m-plex.com/roads/trips/i70et_parkandride.html - bottom), as well as both ends of I-40 ( http://www.interstate-guide.com/i-040.html ) and US 50 ( http://www.geocities.com/usend5059/End050/end050.htm ). Also, signs on the Ohio Turnpike list Chicago ( http://www.roadfan.com/ohtpkchi.jpg ) and New York City "VIA TURNPIKES".

See also 10.3.2 . Mar 25, 2005

3.4.2

3.5 Decommission

3.6 Interchanges

Interchanges are grade-separated intersections with one-way ramps connecting the two roads. They are often also called "exits" though that term may also apply to a single off-ramp (road carrying traffic from the freeway to the crossroad). The many different types are outlined at http://www.kurumi.com/roads/interchanges/ . Hybrid interchange-intersection conditions also exist, such as Jughandles, common in NJ ( http://en.wikipedia.org/wiki/Jughandle ); Michigan Lefts, common in MI ( http://www.michiganhighways.org/indepth/michigan_left.html ), known in Chicago as "Boulevard Turns"; or "channelization". Sep 13, 2005

3.6.1 SPUI

One of the more talked about types of interchanges, a SPUI (single-point urban interchange) looks like a standard diamond interchange, but the ramps work in a much different way, allowing traffic to flow easier by making opposing left turns concurrent. A list is available at http://web.archive.org/web/20021218091949/http://web.mit.edu/spui/www/spui/ (page no longer active). See also http://www4.trb.org/trb/crp.nsf/All+Projects/NCHRP+3-40 / http://64.118.69.9/acb1/showdetl.cfm?DID=92&Product_ID=2277 ("Single Point Urban Interchange Design and Operations Analysis", National Cooperative Highway Research Program [NCHRP] Report 345) as well as Section 2 . Mar 11, 2006

3.6.2

A: In the U.S., there are 51 miles southbound and 49 miles northbound between Exit 193 (US-441/FL-60) and Exits 242/244 (US-192/441), and 41 miles between Exit 152 (FL-70) and Exit 193, on Florida's Turnpike. There are 37 miles between Exit 4 (Bonneville Speedway) and Exit 41 (Knolls) on I-80 in western Utah, the longest stretch on both a free highway and a publicly-numbered highway (Florida's Turnpike is officially FL-91 but there are no references to that in the field). There are also no services between these two I-80 exits, just a pair of rest areas (the two Florida's Turnpike stretches listed above both have a median service area along them). See Question 6.10 for the longest stretch between services on an Interstate and Question 6.10.1 for the longest stretch on an Interstate between other Interstates. Jun 10, 2005

3.6.3 Exit Lists

An exit list, also called an exit guide, is a listing of all the exits on a section of freeway/tollway/expressway. It is used to find the information about an exit before one exits. Sometimes exit lists are also made for surface streets with some degree of access control (for example arterials with jughandles in New Jersey). The exit lists are typically made by people who want to make them (roadgeeks). They use maps and personal experience when creating the exit guide. A few state departments of transportation make bare-bones text exit lists. Some of the exit lists have services listed at exits, while others just list the exits. Most list the cities and towns the exit leads to. Rest areas are usually listed. Some of the service area listings even include what types of food and gas (petrol) establishments may be found at those service areas (service plazas/oases). Links to exit lists are at http://www.ajfroggie.com/triskele/ . Nov 18, 2003

3.6.4 Interchange names

Alemany Maze: I-280 @ US 101, San Francisco
Anjou: A-40 @ A-25, Montreal
The Apex: I-75 @ I-275 (north junction), Metro Tampa/St. Petersburg, FL
Basketweave: ON 401's collector lane/local lane exchange near Jane Street, Toronto
The Big I: I-25 @ I-40, Albuquerque
The Big I: I-10 @ I-95, Jacksonville
The Big Scramble: I-24 @ I-124 (US 27), Chattanooga, TN
The Big Split: I-94 @ I-494 (W), Metro Minneapolis/St. Paul
The Big X: I-74 @ I-80 (E), near Moline, IL (Metro Quad Cities, IL/IA)
Blue Water Tower Interchange: I-90 @ I-290, Metro Buffalo
Braintree Split: I-93 and US 1 @ MA 3, Braintree
Brookwood Interchange: I-75 @ I-85 (north junction), Atlanta
Bruckner Interchange: I-95 @ I-295 @ I-278 @ I-678, New York
Can of Worms: I-490 @ I-590/NY 590, Rochester
Capitol Interchange: I-35E @ I-94, St. Paul
Circle Interchange: I-90/94 @ I-290, Chicago
Cloverleaf: I-77 @ I-480, Metro Cleveland
Crossroads of Mid-America: I-55 @ I-80, Joliet, IL
Crosstown Commons: MN 62 @ I-35W, Minneapolis
Dallas High 5: I-635 @ US 75, Dallas
Dead Man's Curve: I-90 @ OH 2, Cleveland
Dead Man's Curve: I-65 @ I-70 (north junction), Indianapolis
Decarie: A-40 @ A-15 @ QC 117, Montreal
East Los Angeles Interchange: I-5, I-10 and US 101 @ CA 60, Los Angeles
Edens Junction: I-90 @ I-94 (north split), Chicago
El Toro Y: I-5 @ I-405, Irvine, CA - its often-cited 26-lane width contains roadways of both highways (see also 12.3)
Elkhorn Interchange: I-5 @ CA 99 (north junction), Metro Sacramento
Fish Bowl: I-15 @ I-215, Las Vegas
Fishhook: CA 1 @ CA 17, Santa Cruz
Flying Wye: I-84 @ I-184, Boise
Fountain Interchange: US 41 @ FL 82, Ft. Myers
The 4-Level: US 101 @ I-110, Los Angeles (adjacent to the Slot on US 101)
Freeman Interchange: QEW @ ON 403 @ ON 407, Burlington
Golden Glades: I-95, FL 826, US 441 and FL 9 @ Florida's Turnpike, North Miami Beach
Grandview Triangle: I-435 and US 71 @ I-470, Kansas City
Halawa Interchange: H-1 @ H-3, Metro Honolulu
Henderson Spaghetti Bowl: I-215 @ I-515 (UC), Metro Las Vegas
Highbridge Interchange: I-87 @ I-95, New York
Hillside Strangler: I-88 @ I-290 @ I-294, Metro Chicago
Jacques-Cartier: A-20 @ QC 132 and QC 134, Montreal
The Junction: I-196 @ US 131, Grand Rapids (See also 12.1)
The Junction: I-276 @ I-476, Metro Philadelphia
Kew Gardens Interchange: I-678 @ Grand Central Pkwy @ Robinson Pkwy, New York
Lemoyne: QC134 @ QC 112 @ QC 116, Montreal
MacArthur Maze (officially Distribution Structure): I-880 and I-80 @ I-580, Oakland
Malfunction Junction: I-75 @ OH 4, Dayton
Malfunction Junction: I-275 @ I-4, Tampa
Malfunction Junction: I-20/59 @ I-65, Birmingham (AL, US) (See also 12.1)
Malfunction Junction (old): I-40 @ I-275 (former I-75), Knoxville
Malfunction Junction: I-26 @ I-126, Columbia
Malfunction Junction: I-40 @ I-85, Greensboro, NC
The Merge or The Split: I-94 @ I-57, Chicago
The Merge: I-96 @ US 131 (part), Grand Rapids
Midtown Interchange: I-95 @ I-395, Miami
Mixing Bowl: I-5 @ Atlantic Blvd., East Los Angeles
Mixing Bowl: I-696 @ US 24 and MI 10, Southfield (Metro Detroit)
Mixing Bowl: I-96 @ I-96/275 @ I-696 @ MI 5, Farmington Hills/Novi (Metro Detroit)
Mixing Bowl (old): I-395 and VA 27, Arlington
Mixing Bowl: I-95 and I-495 @ I-395, Springfield, VA
Mixmaster: I-30 @ I-35E, Dallas
Mixmaster: I-84 @ CT 2, East Hartford (aka East Hartford Interchange)
Mousetrap: I-25 @ I-70, Denver
North Mixmaster: I-35/80 @ I-235 (N), Des Moines
NW 27th Interchange: I-95 @ I-195, Miami
Oak Park Interchange: US 50/BL I-80 @ CA 99, Sacramento
The Octopus (intersection, extensively rebuilt 1997-'98): NY 13 @ NY 13A @ NY 79 @ NY 89 @ NY 96, Ithaca (42.44,-76.515 ; http://www.14850.com/web/octopus/ )
Orange Crush: I-5 and CA 22 @ CA 57, Orange
Riverside Junction: I-215 and CA 60 @ CA 91, Riverside
St.-Hubert: QC 112 @ QC 116, Montreal
San Bernardino Split: US 101 @ I-10, Los Angeles
Short Stack: I-10 @ AZ-51 @ AZ-202, Phoenix
The Split: I-80 @ BR-80 and CA 244, Sacramento
The Split: See "The Merge"
The Stack: I-84 @ CT 9, Newington
The Stack: I-55 and I-20 @ US 49, Jackson, MS
The Stack: I-10 @ I-17, Phoenix
Spaghetti Bowl: I-15 @ I-515, Las Vegas
Spaghetti Bowl: I-80 @ US 395, Reno
Spaghetti Bowl: I-10 @ I-110, El Paso
Spaghetti Bowl: I-30 @ I-35, Dallas
Spaghetti Bowl: I-64 @ I-264, Metro Norfolk (?)
Spaghetti Bowl: I-65 @ I-70 (N), Indianapolis
Spaghetti Bowl: I-80 @ US 46 @ NJ 23, Wayne
(See also Henderson Spaghetti Bowl)
Spaghetti Junction: I-35W @ I-94 @ MN-55, Minneapolis
Spaghetti Junction: SH 1 @ SH 16, Auckland, New Zealand
Spaghetti Junction: H1 @ HI 92, Honolulu
Spaghetti Junction: I-85 @ I-285 (NE), Metro Atlanta
Spaghetti Junction: I-64 and I-65 @ I-71, Louisville
Spaghetti Junction (formally Gravelly Hill interchange): M6 @ A38(M), Birmingham, West Midlands, England

Hawaii generally names all interchanges, and many toll highways name their interchanges as well.

See also http://en.wikipedia.org/wiki/Category:Named_interchanges

Feb 20, 2007

3.6.5 Volleyball

An interchange between two roads whose ramps meet at at-grade intersections on a third level, those at-grade intersections being the only ones in the interchange. Not an official term. See http://www.kurumi.com/roads/interchanges/volleyball.html Jan 3, 2003

3.6.6 One-quadrant ramp

As named by AASHTO (see Question 4.2) in their "Green Book", aka A Policy on Geometric Design of Highways and Streets (2001 edition: Publication Code GDHS-4, ASIN 1560511567), this describes a simple two-way connecting road between two main roads which themselves are grade-separated. While it is identified as an interchange and displays a main characteristic of one (the separation), it is unusual in that all eight turn movements traverse two at-grade intersections, one at each end of the connector (unless right-turn ramps at one or both of the intersections are employed), whereas generally at least one of the main roads in an interchange only connects to the other with sharp-angled offramps that do not allow cross traffic.
A sampling of locations of these is located at http://groups.google.com/group/misc.transport.road/browse_frm/thread/29557225ca80a680 Aug 12, 2004

3.6.7 Truck escape ramps

A discussion of escape ramp construction/composition and locations is at http://groups.google.com/group/misc.transport.road/browse_frm/thread/2999858fb0a6548 (6/30/05), and signage standards are at http://mutcd.fhwa.dot.gov/HTM/2003r1/part2/part2c.htm#section2C13 . Jul 19, 2005

3.7 Jersey Barrier

A concrete divider on freeways with a cross-section in the shape on an inverted Y. More information is available at http://www.roadstothefuture.com/Jersey_Barrier.html .

3.8 Mileposts

Mileposts are signs placed every mile on roads which show the mileage from some point along the route (usually a terminus or a political boundary.) The MUTCD standard is to use a green vertical sign with the word "MILE" at the top. Some states use them only on Interstates; others put them on other routes as well. California restarts its mileposts (which it calls postmiles) at each county line, including interstates. Many other states do this too, but not for interstates. Kilometerposts are used in places using kilometers. Images are at http://members.aol.com/rcmoeur/d10.html and http://mutcd.fhwa.dot.gov/HTM/2003/part2/fig2d-13_longdesc.htm . There is also a 1967 publication by the Insurance Institute for Highway Safety called "Mileposting". See also 10.3.1 and 10.3.2 .

3.9 Multiplex

When two routes "join up" and are co-signed. Other similar terms used are "concurrency" and "overlap" ("multiplex" seems to be a creation of m.t.r while the others are actually used by DOTs). A secret multiplex occurs when one route is unsigned on the concurrent section. A useless/unnecessary multiplex occurs when one or both of the routes ends while multiplexed; one of them could have ended at the other. A wrong-way multiplex occurs when the 2 routes are signed in opposite directions (e.g. [NORTH] [1]/[SOUTH] [3]). A wrong-way multiplex may also carry a route with a third direction (e.g. [NORTH] [1]/[SOUTH] [3]/[EAST] [2]) - there are many examples of this in the field in various places. A four-direction multiplex is theoretically possible (some individual routes can and do briefly run in or close to the opposite direction of which they are signed, see Question 12.16.1 ) but none has been found yet by m.t.r contributors.

RI-114 actually multiplexes with itself in Pawtucket (it is a transition between two one-way couplets where one couplet has each direction with the oncoming route to the left rather than to the right, due to a circuitous path taken by the northbound routing). See http://en.wikipedia.org/wiki/Rhode_Island_Route_114#endnote_Pawtucket .
Truck US-19 also does this while traversing a pair of I-279 interchanges in Pittsburgh. http://www.m-plex.com/roads/pamplex/mp_i279_us19_trkus19_us22_us30.html#19
US-250 may also do this at US-19 in Fairmont, WV.

A more detailed guide on multiplexes is located at http://www.m-plex.com/roads/mpguide.html . Mar 8, 2007

3.9.1

A: I-465 on the east side of Indianapolis, IN, between the US-36/SR-67 and US-40 exits, also carries US-31, US-36, US-40, US-52, US-421, SR-37, and SR-67, for a total of 8 routes on one highway, though only I-465 is posted along this stretch as all other routes following I-465 except I-74 have a sign reading "FOR [route shield][direction]/FOLLOW [I-465 shield]/to Exit [number]" on the onramps where they enter I-465 (see http://illi-indi.com/showFull.php?id=1452§ion=34652 ). The most signposted routes is 7 in GA: US-1, US-23, US-301, SR-4, SR-15, SR-23, and SR-121 just short of the FL line ( http://www.gribblenation.com/papics/outofstate/gatotempole-folkston.jpg ). This is possible because in GA every US highway is usually paired with at least one signposted state route (see 7.6.4 ), so other examples with this many or possibly even more may exist elsewhere in the state.

For Interstates the most along any one roadway is

I-55/64/70 between St. Louis, MO, and East St. Louis, IL (FHWA implies in its route log [see Section 6 intro] that I-44 ends at I-70, but MoDOT states that it goes to the IL border, creating by that reckoning I-44/55/64/70, though this may change with the construction of a new Mississippi R. bridge further north [ http://www.newriverbridge.org/ ]),

and I-39/90/94 in WI.

(In OH, I-77/80/90 and I-77/80N/90, portions of today's I-80/90 and I-90, were briefly proposed when the easternmost portion of today's I-94 was to be the northernmost portion of I-77, but these were never signposted - see http://www.roadfan.com/5758int.html .)

For U.S. highways, it's a tie between many four-route multiplexes, including that on the aforementioned I-465 segment. (US-61/63/64/70/79 used to run on I-55 between West Memphis, AR, and Memphis, TN, possibly with US-63 ending at the AR/TN line, but US-63 was later rerouted.) Sep 13, 2005

3.10 Ramp to Nowhere

Segments of highway or ramp that sit unused, often barricaded. They may be part of a cancelled or a future highway project. Also called Ghost Ramps. A special type is the Evel Knievel Ramp, which stops in mid-air. See http://en.wikipedia.org/wiki/Unused_highway Feb 8, 2007

3.11 Roadgeek

Usually used to mean an m.t.r regular who is not professionally involved with roads. Also used to describe anyone who has a larger-than-average interest in roads. Other similar terms used are "roadfan", "highway enthusiast", "viaphile", "odologist" (see http://www.cbrd.co.uk/reference/dictionary/#o ), and the pun "roads scholar". See http://web.archive.org/web/20040414215828/http://www.ylekot.com/geek.html (no-longer-extant webpage at Archive.org)

A list of roadgeeks by location is at http://www.roadfan.com/roadfan.html . A collection of photographs from various roadgeek meetings is at http://www.prism.gatech.edu/~gtg377a/meetings.html . Mar 10, 2006

3.12 Super 2

3.13 Toll highway

A freeway that charges a toll. Some people on m.t.r do not use "freeway" to describe a toll highway (see also 3.14). Various states refer to these with various names. Lists of toll facilities are available at http://www.fhwa.dot.gov/ohim/tollpage.htm and http://www.contrib.andrew.cmu.edu/~mn2n/tollroads.html . In the 1800s toll roads were known as Turnpikes (see http://eh.net/encyclopedia/?article=Klein.Majewski.Turnpikes ), a term which resurfaced in the middle of the 20th Century. Interstates specifically may be tolled only if physical improvements are made to them (in which case the toll is used to pay for the improvements), there is reimbursement to the Federal Highway Administration all federal money used in the building process of the stretch in question, or there is an Act of Congress. See also http://www.tollroadsnews.com/ . Mar 8, 2007

3.13.1 E-ZPass

This is one of many Electronic Toll Collection agencies in North America. Go to http://www.e-zpass.info/ for a list and map of E-ZPass-compatible highways, and http://www.e-zpassiag.com/ for a list of all the ETC agencies worldwide as well as contact information. The term "open-road tolling" is used to describe the condition using this system in which motorists do not have to slow to below highway speed to be detected. Apr 5, 2007

3.14

A: According to AASHTO, a freeway is a fully controlled access road, one with no cross traffic. A freeway can be tolled; the "free" refers to the fact that traffic can ideally flow freely. An expressway is a divided highway with no private access BUT occasional traffic lights are allowed; essentially it is a freeway with intersections, usually with traffic signals, in place of interchanges. Major roads should get interchanges where traffic necessitates them. Many states, including California and Wisconsin, use this. This FAQ does too.
However, most east coast states plus others use expressway for the "official" freeway, and freeway is simply an alternate term for the same thing, or absent from the vocabulary altogether. Many of these states use the "official" terms in legal matters but name them differently. There are two cases of an "official" expressway being named a freeway: the Rockaway Freeway in New York City and the State Fair Freeway (K-96) between Wichita and Hutchinson, Kansas.
A special type of expressway is the "Jersey Freeway", an unofficial term used to describe an expressway with no median breaks. As the name implies, these are common in NJ.
For a list of expressways in the US and Canada see http://www.expresswaysite.com/ .

"Limited access" usually refers to freeway grade in common usage; according to AASHTO, however, only "controlled access" refers to freeway grade, whereas "limited access" refers to expressway grade. Some states including FL reverse AASHTO's definitions, and some states such as VA use "limited access" to designate only frequency of access and not specifically highway type.

See also http://en.wikipedia.org/wiki/Freeway and http://en.wikipedia.org/wiki/Expressway . Jul 18, 2006

3.14.1

A: It depends on the local region's tradition. OR actually uses both terms in different contexts (see Question 7.6.4). The term "the" preceding the route number (e.g. "the 405") is only common in S. CA ( http://groups.google.com/group/misc.transport.road/browse_frm/thread/a7a6b7d8190d5ade ) and metro Buffalo within the US (it is common in other English-speaking countries). Discussions on the topic: http://groups.google.com/group/misc.transport.road/browse_frm/thread/63541a08acbb25df ; http://groups.google.com/group/misc.transport.road/browse_frm/thread/450c1b829e05b5f6 ; http://groups.google.com/group/misc.transport.road/browse_frm/thread/777d51fb2d8bf9a4 Oct 21, 2004

3.15 Spur

3.16

A: Very generally, roundabouts are small circular roadways built for traffic flow improvement which are designed more meticulously than traffic circles, which sometimes are just the roadway around an obstruction rather than dedicated traffic control. For very detailed information, see http://www.tfhrc.gov/safety/00-0671.pdf , especially Section 1.5 (this is part of http://www.tfhrc.gov/safety/00068.htm ), as well as http://mutcd.fhwa.dot.gov/HTM/2003r1/part3/part3b2.htm#section3B24 . See also http://dmoz.org/Recreation/Roads_and_Highways/Interchanges/Roundabouts/ and http://www.aaroads.com/kick-off/highway.html#roundabout . (Note that some newer traffic circles are not roundabouts, but small "traffic-calming" devices - see http://dmoz.org/Science/Technology/Transportation/Traffic_Calming/ .)

Roundabouts are often used in Great Britain at interchanges, either as a large roundabout ( http://www.cbrd.co.uk/reference/interchanges/roundabout.shtml ) or two smaller ones on each site of the motorway ( http://www.cbrd.co.uk/reference/interchanges/dumbbell.shtml ). The latter is also gaining presence in the U.S., most notably along I-135 in KS, and on I-70 in Vail, CO. Other locations are listed at http://groups.google.com/group/misc.transport.road/browse_frm/thread/fbba5dca747aa3ec (10/17/05).

The term "rotary", found mostly in MA, may refer to either a traffic circle or a roundabout.

The term "roundabout" originated in Great Britain, but is purported to have been coined by an American working abroad there ( http://groups.google.com/group/misc.transport.road/msg/85bb8a44f40b98e9 , message ID 1127264917.495082.158470@g49g2000cwa.googlegroups.com ). Dec 15, 2005

3.16.1

A: There are many. The most famous of these is located in Swindon in southern England, and is a roundabout containing five mini-roundabouts within it. The main roundabout carries two-way traffic. For more information, see http://www.swindonweb.com/life/lifemagi0.htm and http://www.digitalnorseman.com/musings/2002/rndabt.html . A compilation of locations of these roundabouts is located at http://www.pberry.plus.com/ukroads/magicroundabouts/ . Apr 8, 2003

3.17 Bump

This is a term used on m.t.r to describe two routes which resume each other's routings at an intersection, only overlapping within the intersection (ex.: a route which enters an intersection from the west and leaves to the north, and another which enters the same intersection from the south and leaves to the east). This term is also applied to freeway interchanges, even if the routes in question actually cross each other or have a short overlap within the interchange (exs.: I-80/eastern I-76, I-80/I-74). "Cannon" has been suggested as a British equivalent (http://www.cbrd.co.uk/reference/dictionary/#c ). Apr 23, 2005

3.18 Cutout

This refers to a route marker (see Question 10.1) which is cut in its own shape, rather than cut as a square or rectangle with a black background behind the marker shape. All route markers were originally cutouts, and today most Interstate and some state route shields are cutouts, as well as US shields in various places, predominantly CA (see http://www.ugcs.caltech.edu/~jlin/signs/usa/#US ). Jul 19, 2005

3.19 Clinch

To travel a highway its entire length. This definition is tempered by personal interpretations, such as travelling both directions, traversing ramps, driving vs. riding, and completing in a single trip. See http://cmap.m-plex.com/ and http://www.aaroads.com/clinched/ . Mar 8, 2007

Other road terms are listed at http://www.aaroads.com/glossary.html . A parody list of terms is at http://www.kurumi.com/roads/bierce.html . Jan 27, 2005

4 Government

Highways are covered in the respective Section 23s of both the U.S. Code ( http://www.access.gpo.gov/uscode/title23/title23.html ) and the Code of Federal Regulations (U.S.) ( http://www.access.gpo.gov/cgi-bin/cfrassemble.cgi?title=200523 ). Mar 10, 2006

4.1

A: The Federal Highway Administration (http://www.fhwa.dot.gov/) is an agency of the U.S. Department of Transportation that administers funding for American highways, including the National Highway System (see Question 7.7 ). It also promotes safety on the highway system. Links to online manuals and articles published by the FHWA (including the MUTCD, see Section 10 ) are on http://www.fhwa.dot.gov/fhwaweb.htm (see also Section 10). Note that the abbreviation for the agency is not "FHA" (which is the Federal Housing Administration). Also note that the National Highway Traffic Safety Administration (NHTSA) is not a part of FHWA (but is a part of the USDOT), nor are the Transportation Security Administration (TSA) (formerly but no longer part of the DOT) or the National Transportation Safety Board (NTSB). Mar 11, 2006

4.2

A: The American Association of State Highway and Transportation Officials (http://www.transportation.org/) is a consortium of the 50 state DOTs and USDOT. Formerly known as AASHO. Documents with route numbering decisions made by AASHTO since 1989 are located on the Special Committee on U.S. Route Numbering page at http://cms.transportation.org/?siteid=68 . Dec 8, 2005

4.3

A: ISTEA, the Intermodal Surface Transportation Efficiency Act, passed in 1991, authorized federal funding for highway, transit and safety programs. The funding expired in October 1997, so in March 1998, ISTEA was given an extension. TEA-21, the Transportation Equity Act for the 21st Century ( http://www.fhwa.dot.gov/tea21/ ), which can be viewed as a successor to ISTEA, authorizes a 33% increase in transportation spending. They also include regulations which must be followed to receive federal funding. The next successor, passed in 2005, is SAFETEA-LU, the Safe, Accountable, Flexible, and Efficient Transportation Equity Act: A Legacy For Users, known prior at different times as SAFETEA or TEA-LU ( http://www.fhwa.dot.gov/safetealu/ , http://www.house.gov/transportation/highway/tealu.html , or http://www.house.gov/transportation/highway/increasehighwayfund.html ). A list of corridors is at http://www.aaroads.com/high-priority/ and http://www.fhwa.dot.gov/hep10/nhs/hipricorridors/ . Sep 13, 2005

4.4

A: The Appalachian Regional Corridors are a system of proposed 4-lane highways designed to stimulate economic development in the Applachian Mountain Region. They each have letters. For more information see http://www.arc.gov/index.do?nodeId=1006 and http://www.aaroads.com/arc/ (the latter has a chart of corridor letters and corresponding route numbers). Jan 14, 2002

5 Websites

Links to road websites are available at
http://dmoz.org/Recreation/Roads_and_Highways/ (alternate URL: http://roadlinks.cjb.net/ ),
http://www.aboutvia.com/ (alternate URL: http://www.ugcs.caltech.edu/~jlin/links/ ),
http://www.aaroads.com/kick-off/highway.html , and
http://www.cahighways.org/othlinks.html .
(All of these are listed at http://dmoz.org/Recreation/Roads_and_Highways/Directories/ .)

See also the Wikipedia "Road" entry and related subarticles at http://en.wikipedia.org/wiki/Road as well as the US Roads Portal at http://en.wikipedia.org/wiki/Portal:U.S._Roads .

Mar 10, 2006

6 The Interstate Highway System

The Interstate Highway System (or, more formally, the Dwight D. Eisenhower National System of Interstate and Defense Highways) is a system of divided controlled access highways present in every state as well as DC and PR. It has more than 45,000 miles to its credit. A complete list is found at http://www.ihoz.com/interstates.html (1 and 2 digit) and http://www.kurumi.com/roads/3di/ (3 digit), as well as at http://www.interstate-guide.com/ . Information on planned Interstates and Interstate extensions can be found at http://www.aaroads.com/high-priority/ and http://www.interstate-guide.com/future.html . FHWA's overview of the system is at http://www.fhwa.dot.gov/programadmin/interstate.html , a route log is at http://www.fhwa.dot.gov/reports/routefinder/ , and an FAQ is at http://www.fhwa.dot.gov/interstate/faq.htm . See Question 6.1 for Interstate history. The U.S. Code of Federal Regulations lists in Title 23, Appendix A to Subpart A of Part 470, the "Guidance Criteria for Evaluating Requests for Interstate System Designations Under [Title] 23 [of the] U.S. [Code, now-repealed Section] 139 (a) and (b)" (for text, see the portion directly after Section 470.115 in the respective file at http://www.access.gpo.gov/nara/cfr/waisidx_04/23cfr470_04.html ). AASHTO's Interstate policy is at http://www.trafficsign.us/inpolicy.html . This policy states among other items that Interstates and U.S. Highways with the same number should not exist in the same state, likely the reason why there is no I-50 or I-60, although US-24 and I-24 both exist in IL, and US-80 and I-80 briefly existed in CA until the former was truncated outside the state (both instances presumedly overlooked due to the distance between), and three proposed Interstate extensions and one new Interstate are planned to exist in states with the corresponding U.S. route (41 in WI, 49 in AR, 69 in TX, 74 in NC - on current signage for the latter's pairing with US 74, "FUTURE" replaces "INTERSTATE" on the I-74 shields - see elsewhere in Section 6 for more details on each of these).
Even though these routes are known as being federally-marked routes, it is actually the states that maintain them in most cases, and other non-federal-level agencies in the rest. The Interstates have received federal funding of various percentages of the whole throughout the history of the system, however (see http://www.cahighways.org/itypes.html ). Interstates are automatically included in the National Highway System (see Question 7.7 ).
There are single-state Interstates (see Question 6.12) - the name "Interstate" refers to the system as a whole and not to any individual numbered route.
A ranking subject to interpretation of 2-digit Interstates by importance is located at http://www.kurumi.com/roads/rank2di.html .
For business route information see 3.2. Mar 10, 2006

6.1 Interstate History

http://www.fhwa.dot.gov/infrastructure/history.htm includes many historical articles, and http://www.interstate50th.org/ has been set up by AASHTO and includes much historical information. See also Section 17.

6.1.1

A: In 1944, Congress authorized construction of an interstate expressway system connecting major cities and industrial centers. No money was involved in the bill. The project never took off until the awarding of the first contract for I-70 in Missouri, in 1956. North Dakota was the first state to complete its Interstates. More information is available at http://www.tfhrc.gov/pubrds/summer96/p96su10.htm and http://eisenhower.archives.gov/dl/InterstateHighways/InterstateHighwaysdocuments.html . Jul 10, 2003

6.1.2

A: The first stretch of Interstate opened under the 1944 Congress act was I-70 in Kansas, which opened in 1957. More information is at http://www.tfhrc.gov/pubrds/summer96/p96su18.htm 2000-08-17 15:29:33

6.1.3

A: The Interstate System's original plans are detailed in a publication called General location of national system of interstate highways, including all additional routes at urban areas designated in September, 1955, commonly known as the "Yellow Book". Go to http://www.ajfroggie.com/roads/yellowbook/ or http://www.roadfan.com/intreg.html#yellowbk for much more information including maps. See also http://www.roadfan.com/5758int.html . Apr 5, 2007

6.2 Interstate Numbering

There's a very strict plan for numbering Interstate routes. The one and two-digit routes are the mainlines, with the even numbered routes going east-west, and the odd routes going north-south. The even routes' numbers increase as you go north, with the odd Interstate roads increasing to the east. The major routes end in 0 or 5. As for three-digit interstates, those that both start and end at a 2-digit route get an even first digit, while those not connected to the Interstate system at their end or ends have an odd first digit. Exceptions to this occur usually when a state has depleted its respective choices for 3-digit Interstates. If a 3-digit Interstate has another 3-digit Interstate branching from it (a "grandchild"), then the numbering for the second-generation highway is the same as for the first-generation one. In the field are I-105 CA, I-235 KS, I-444 OK, I-370 MD, I-175/375 FL, I-278/478/678/878 NJ/NY, I-579 PA, I-280/380/980 CA, I-190 MA, I-590/990 NY, I-495 NY, I-695 DC, and I-795 MD (each intersects with another 3di with a common "root" but not with its 2di parent). I-195 NJ also used to be one but it now intersects I-95 directly. For more on numbering see the FHWA site at http://www.fhwa.dot.gov/programadmin/interstate.html#Interstate_Numbering .

Documents with Interstate route numbering decisions made by AASHTO since 1989 are located on the Special Committee on U.S. Route Numbering page at http://cms.transportation.org/?siteid=68 . Dec 8, 2005

6.2.1 Letter Suffixes

6.2.1.1

A: AASHTO eliminated them in 1980 and told state DOTs to think of other numbers. Two still remain on I-35. I-15E in California stayed until 1983 (see 6.2.1.3). Jan 18, 2002

6.2.1.2

6.2.1.3

I-5W (CA) -- I-505, I-80, I-580, I-205, CA-120 (see http://www.cahighways.org/001-008.html#005 for details)
I-15E (CA) -- I-215 (see http://www.cahighways.org/009-016.html#015 , section 2, for details)
I-15W (ID) -- western I-86
I-24W (MO/TN) -- I-155 and US 412
I-35W/I-35E still exists in TX and MN (see 6.2.1.2)
I-35W (KS) -- I-135
I-59B (AL) -- I-459 (Note: "59B" was chosen through a system of placeholder numbers using "A", "B", etc., as opposed to "B" meaning "bypass")
I-70N/I-70S (MD) -- I-70/I-270
I-70S (PA) -- I-70 between I-79 and I-76
I-75E (FL) -- I-75 between I-275 termini
I-80N (OR/ID/UT) -- western I-84
I-80N (IA) -- I-680 east of I-29
I-80N (OH) -- I-80/90, I-90, I-490, I-480, and OH 14 between US 250 near Norwalk and I-76 near Ravenna
I-80S (CO/NE) -- western I-76
I-80S (OH/PA/NJ) at first used today's I-76 in OH and PA and I-276 in PA; later it was rerouted on today's I-76 and I-676 through Philadelphia and Camden rather than around; and later it was truncated at today's I-376 when I-76 was created along today's I-376 and the PA Turnpike
(See http://www.roadfan.com/ohiomaps.html , http://www.pahighways.com/interstates/pdi.html#I80S , and http://www.fhwa.dot.gov/infrastructure/i76.htm for details on the OH/PA/NJ I-80N/I-80 and I-80/I-80S)
I-81E (PA) -- I-380
I-180N (ID) -- I-184 in Boise; all other spurs of suffixed 2dis were non-suffixed

Planned but never signed

The sources for these are the 1957 and 1958 maps on http://www.roadfan.com/5758int.html -- see 6.1.3 for more details

I-5E (CA) -- I-5 between I-5W termini (see above)
I-80N (PA/NJ) -- I-78
I-80S (PA) -- I-76 east of Harrisburg
I-81S (PA) -- I-81E (see above)
I-82N (ID) -- I-15W (see above)
I-82S (ID/UT) -- I-80N between I-15W (see above) and I-15
I-90N (NY) -- I-190
I-94N (MI) -- I-196 (now I-96 west of Grand Rapids)
I-95E (RI/MA) -- I-195 (pre-Interstate plans called it US 6)

Sep 13, 2005

6.2.2

More information is available at http://www.pahighways.com/interstates/I99.html . Oct 3, 2004

6.2.3

A: Interstate 238 is a 2-mile freeway on the east side of San Francisco Bay, California. It is not numbered according to the regular Interstate numbering conventions; rather, it was an extension of CA 238. There is no I-38. More information is at http://www.gbcnet.com/roads/I-238/ . May 28, 2002

6.2.4

A: All duplicates but 86 arose around the time when most letter suffixes on Interstates were removed, though not all replaced a suffixed Interstate designation. Eastern I-86 (see 6.3.6) was recently added because there were no other choices that would fit. At one time, an eastern I-86 existed from Hartford, CT to I-90 in MA; this is now part of I-84 (see http://www.kurumi.com/roads/ct/i86.html ). There were also two I-39s, but I-39 is now signed along I-90 between the two sections (see http://www.interstate-guide.com/i-039.html ). There are technically two I-74s, but these are planned to be connected, unlike the other duplicates (see Question 6.3.4 ). I-90, interpreted by some two be in two segments, is actually continuous (see Question 6.3.10 ). At one time two I-77s and two I-82s were planned (see http://www.roadfan.com/5758int.html ). Apr 5, 2007

6.2.5

6.3 Oddities

6.3.1

A: The short explaination is the "NIMBY factor". Residents of the Princeton and New Brunswick, NJ, areas managed to kill a section of I-95 through their towns in the early 1980s; the NJ Turnpike also opposed it as it would provide an alternate to the toll road. There has been a gap ever since. On the NJ Turnpike, the I-95 signs disappear. There is a plan to build an interchange connecting the existing I-95 with the PA Turnpike northeast of Philadelphia, where they currently cross but do not have an interchange. The new routing would follow the PA Turnpike connector from the NJ Turnpike across the Delaware River to the new interchange, where it would resume its old route. This interchange should be complete around 2008. More information is available at http://www.njfreeways.com/Interstate_95_Gap.html , http://www.nycroads.com/roads/I-95_NJ/ , and http://www.paturnpike.com/i95/ . This will complete the gap between New York City and Philadelphia, but will not provide easy access to I-287 from Philadelphia for bypassing New York City as original I-95 would have.
Some propose rerouting I-95 on the NJ Turnpike all the way to the Delaware Memorial Bridge and I-295; this is how most through traffic goes anyway. Many people have a problem with this because it would bypass Philadelphia. Sep 30, 2004

6.3.1.1

A: No. Those numbers are based on the original mileage of I-95 in NJ including the unbuilt portion mentioned above in 6.3.1 (see the relevant section of http://www.nycroads.com/roads/I-95_NJ/ ). Sep 30, 2004

6.3.2

A: Usually Interstates are not allowed to have any cross traffic. In fact at-grade intersections have kept the new I-86 in New York from extending further east. But in these cases, AASHTO granted variances because there was no other reasonable way to build them.
Wyoming I-180 is the only Interstate with no freeway portions. There are three stoplights. Why was it commissioned in the first place? The state of Wyoming wanted an Interstate serving downtown Cheyenne. It was to be freeway, but that idea was rejected. More information is at http://www.rockymountainroads.com/wyoming/i-180.html
I-676 in Philadelphia, PA has some traffic lights between the Vine St Expressway and the Ben Franklin Bridge. Construction of a freeway connection would impact several historic landmarks. There is some doubt among roadgeeks as to whether I-676 actually goes this way; the official PennDOT maps label the freeway connection to I-95 as 0676 and put US 30 on the Ben Franklin Bridge. There is an I-676 shield on the county map, but shields reflect actual signage, not internal designations (as the 0676 does). NJDOT however takes I-676 over the bridge officially and in signage. (See http://www.pahighways.com/interstates/I676.html)
I-78 in Jersey City, NJ runs along a one-way pair of surface streets between the end of the Turnpike Extension and the Holland Tunnel. I-78 ends just across the border in Manhattan, New York City, so it could be truncated, but hasn't been. NJ 139 also runs along those streets, as if NJDOT were prepared for truncation. FHWA, NJDOT, and NYSDOT all officially refer to these last few miles as I-78. (See also 12.2 ) Rehabilitation on an adjacent section of NJ-139 started in 2005 ( http://www.state.nj.us/transportation/commuter/roads/jcviaducts/ ), but this does not affect the at grade section of I-78 (which also carries anotehr section of NJ-139).
I-70 in Breezewood, PA is the most famous of these. It runs along a short section of US 30 lined with businesses between the north-south free portion of I-70 and the Turnpike connection. It would be fairly easy to construct direct ramps, but the businesses have been successful in blocking them. Some think the influential congressman Bud Shuster has helped block the ramps. (See 3.1 above)
I-585 in Spartanburg, SC is signed NB before the freeway starts, past several traffic lights. It is unknown why; the road was and is also US-176. (See 6.3.9)
I-690 at the NY State Fairgrounds in Syracuse has a pedestrian crossing that only functions during the NY State Fair. Because this is only in operation for a small period of time, it is not worth it to build an overpass.
I-8, I-10 and I-17 in AZ, I-40 in NC, I-10 and I-40 in W. TX, and I-40 in NM have some at-grade intersections for forest, farm, and ranch access (see http://www.arizonaroads.com/wrong/). Most of these highways were built directly over a pre-existing rural two-lane road, so this is the only access for many of these properties. Interchanges would not be worth the expense due to the extremely low traffic which these intersecting roads carry (some in fact are private).
AK Interstates have signals, but that is because those Interstate designations are "hidden" along state highways which are usually surface roads with at-grade intersections (see Question 6.3.8 ).

Several other interstates end at traffic lights, but this is perfectly OK as long as this is not a 3di's only connection to its parent or an even 3di's only connection to another interstate at one end.
One example of this that is often brought up is I-587 is Kingston, NY; this connects to the I-87 ramp via a traffic circle. However, a traffic circle is somewhat up to standards; there is no cross traffic.
In fact there is a case of a 3DI not meeting its parent; the abovementioned I-585 in Spartanburg, SC ends at Business Loop I-85, which is the old I-85 (and is a freeway, but not up to full interstate standards). It continues to I-85 (bypass) as 4 lane US 176, which is due for upgrades soon. (See 6.3.9)
I-65 in NW IN formerly had a traffic light installed in 1980 at the IN Toll Road (I-90) connection at the north end (41.592,-87.3) ; this was considered by INDOT to be mainline I-65 ( http://www.in.gov/dot/div/technology/interchanges/I65/is262.pdf - note that this diagram shows the rail crossing just north of the signalized intersection as active; it actually was abandoned by the time I-65 was extended northward to US-12/20) but was not really the same case of a traffic light on an Interstate as other examples because the section north of this signal functioned more like a ramp pair, and was probably considered one by AASHTO. This has been replaced by conventional grade-separated freeway ramps.
I-291 in Springfield, MA, has an access point at I-90/MA Turnpike similar to the former I-65/I-90 junction cited above, albeit with a more simple design (42.16,-72.54).

Several tunnels on the system have signals at their portals, either to stop unwanted vehicles from entering (too tall, too heavy, too wide, hazardous material carrier) or for traffic capacity control.

Question 6.3.7 deals with drawbridges on Interstates, which have traffic lights but no cross traffic.

Railroad crossings:
The Interstate highway specifications do not permit railroad grade crossings. A few did exist before, but all have either been grade separated or had the tracks removed. However, a number of crossings do still exist on some non-Interstate highways with controlled access. In many of these cases, the crossing is classified as "Exempt" by the particular state, meaning that vehicles normally required to stop at railroad crossings, such as vehicles carrying hazardous material and school buses, can continue through without stopping. Instead, all trains are required to send a flagman to clear the highway traffic before it may proceed. These crossings are rarely busy railroad mainlines, as they tend to be lightly-used or even disused industrial spurs. Exempt crossings are noted with a tab on the advance RxR warning sign post and/or on the crossbuck post itself (see http://mutcd.fhwa.dot.gov/HTM/2003r1/part8/part8b.htm#section8B05 ).

Former crossings on Interstates:
I-65 north end in IN (see above). Abandoned, then interchange reconstructed.
I-87 Adirondack Northway, NY, near the Mohawk River. This line was apparently already up for abandonment with the now-defunct Interstate Commerce Commission when the Interstate was being built, so it did not pay to build an overpass that would be useless in a few years.
I-94 near Ypsilanti, MI. Now abandoned. This same line used to cross US 23 at-grade as well.
I-94 near Albion, MI. Now abandoned.
I-395 in N. VA (Shirley Highway) near Glebe Rd. Crossing dismantled when the Washington & Old Dominion RR folded. Note that this was while it had its pre-Interstate designation (VA 350).

Existing crossings on non-Interstate controlled-access highways [* - Exempt]: US-1, Edison, NJ (Jersey Freeway - see 3.14); US-4 near Rutland, VT; US-12/14/18/151, Madison, WI; US-30/250, Wooster, OH*; US-46, Totowa, NJ; US-60, Springfield, MO*; US-63, Columbia, MO; US-151, Beaver Dam, WI; US-151, Waupun, WI; US-301, Rocky Mount, NC; US-322 between Harrisburg and Hershey, PA*; NY-49 near Rome*; OH-7, north of Martins Ferry; OR-22, east of Salem; Atlantic City-Brigantine Connector, NJ*

Other former grade crossings on major divided highways: US-1, Danvers, MA; US-3, Billerica, MA; US-4, Portsmouth, NH; US-6, Denver, CO; US-12/14/18/151, Madison, WI (2 others in addition to the current one); US-23 south of Dundee, MI (and others); US-64, Tulsa, OK (2); US-131, Kalamazoo, MI; MA-2, Concord; NY-17 (Quickway)/future I-86 near Middletown, NY

Note: The above question refers to Interstate intersections with roads which carry general traffic and not roadways such as maintenance roads (intersections between these and freeways are common throughout the U.S.). Mar 11, 2006

6.3.3

A: The Embarcadero Freeway, I-480, would have connected the Bay Bridge to the Golden Gate Bridge in San Francisco, carrying mostly local traffic. The first section north from I-80 was built. Most San Francisco residents hated it because it blocked the view of the waterfront from the other side. After a 1989 earthquake almost made it collapse, it was permanently closed and torn down. The same thing happened to the northern half and most of the upper deck of the Central Skyway (US 101). Across the Bay in Oakland, part of the Cypress Freeway (I-880) actually collapsed, killing some motorists. This double decker freeway was torn down and rebuilt on a new alignment; the old alignment is now a wide boulevard with a park in the middle.
More information is at http://www.cahighways.org/371-480.html#480 and http://www.kurumi.com/roads/3di/i480.html#480ca . Sep 13, 2005

6.3.4