Editing Interstate Highway System (section)

==Signage==

===Interstate shield===
[[File:Texas interstate shield proposals.jpg|thumb|Several Interstate shield design proposals submitted by the Texas Highway Department|alt=Three black and white submissions, the third being similar to the modern Interstate Highway shield]]

Interstate Highways are signed by a number placed on a red, white, and blue [[Highway shield|sign]]. The shield design itself is a [[registered trademark]] of the [[American Association of State Highway and Transportation Officials]].<ref>{{cite web |url = http://tsdr.uspto.gov/#caseNumber=72239199&caseType=SERIAL_NO&searchType=statusSearch |author = American Association of State Highway Officials |date = September 19, 1967 |title = Trademark Registration 0835635 |work = Trademark Electronic Search System |publisher = [[United States Patent and Trademark Office]] |access-date = April 27, 2014 |archive-url = https://web.archive.org/web/20130502074700/http://tsdr.uspto.gov/#caseNumber=72239199&caseType=SERIAL_NO&searchType=statusSearch |archive-date = May 2, 2013 |url-status = dead }}</ref> The colors red, white, and blue were chosen because they are the colors of the [[Flag of the United States|American flag]]. In the original design, the name of the state was displayed above the highway number, but in many states, this area is now left blank, allowing for the printing of larger and more-legible digits. Signs with the shield alone are placed periodically throughout each Interstate as [[reassurance marker]]s. These signs usually measure {{convert|36|in|cm}} high, and are {{convert|36|in|cm}} wide for two-digit Interstates or {{convert|45|in|cm}} for three-digit Interstates.<ref name="SHS">{{Cite book |author = Federal Highway Administration |chapter-url = https://mutcd.fhwa.dot.gov/SHSe/Guide.pdf |chapter = Guide Signs |title = Standard Highway Signs |edition = 2004 English |location = Washington, DC |publisher = Federal Highway Administration |oclc = 69678912 |orig-year = 2004 |date = May 10, 2005 |at = pp. 3-1 to 3-3 |access-date = February 22, 2012 |archive-date = February 5, 2012 |archive-url = https://web.archive.org/web/20120205020037/http://mutcd.fhwa.dot.gov/SHSe/Guide.pdf |url-status = live }}</ref>

Interstate business loops and spurs use a special shield in which the red and blue are replaced with green, the word "BUSINESS" appears instead of "INTERSTATE", and the word "SPUR" or "LOOP" usually appears above the number.<ref name="SHS" /> The green shield is employed to mark the main route through a city's central business district, which intersects the associated Interstate at one (spur) or both (loop) ends of the business route. The route usually traverses the main thoroughfare(s) of the city's downtown area or other major business district.<ref name="MUTCD2D">{{cite book |author = Federal Highway Administration |date = December 2009 |chapter = Chapter 2D. Guide Signs: Conventional Roads |title = Manual on Uniform Traffic Control Devices |chapter-url = https://mutcd.fhwa.dot.gov/pdfs/2009/part2d.pdf |page = 142 |location = Washington, DC |publisher = Federal Highway Administration |oclc = 496147812 |edition = 2009 |title-link = Manual on Uniform Traffic Control Devices |access-date = February 22, 2012 |archive-date = March 15, 2012 |archive-url = https://web.archive.org/web/20120315132420/http://mutcd.fhwa.dot.gov/pdfs/2009/part2d.pdf |url-status = live }}</ref> A city may have more than one Interstate-derived business route, depending on the number of Interstates passing through a city and the number of significant business districts therein.<ref name="MDOT11">{{cite MDOT map |year= 2011 |inset= Lansing |link= yes }}</ref>

Over time, the design of the Interstate shield has changed. In 1957 the Interstate shield designed by [[Texas Highway Department]] employee Richard Oliver was introduced, the winner of a contest that included 100&nbsp;entries;<ref>{{cite magazine |author = Texas Transportation Institute |url = http://tti.tamu.edu/publications/researcher/v41n4/41_4.pdf |title = Ties to Texas |magazine = Texas Transportation Researcher |volume = 41 |issue = 4 |pages = 20–21 |year = 2005 |archive-url = https://web.archive.org/web/20100820082038/http://tti.tamu.edu/publications/researcher/v41n4/41_4.pdf |archive-date = August 20, 2010 |author-link = Texas Transportation Institute }}</ref><ref>{{cite web |author = American Association of State Highway and Transportation Officials |year = 2006 |url = http://www.interstate50th.org/gallery.shtml |title = Image Gallery |work = The Interstate is 50 |publisher = American Association of State Highway and Transportation Officials |access-date = February 22, 2012 |url-status = dead |archive-url = https://web.archive.org/web/20120225170530/http://www.interstate50th.org/gallery.shtml |archive-date = February 25, 2012 }}</ref> at the time, the shield color was a dark navy blue and only {{convert|17|in|cm}} wide.<ref>{{cite book |author = American Association of State Highway Officials |year = 1958 |title = Manual for Signing and Pavement Marking of the National System of Interstate and Defense Highways |location = Washington, DC |publisher = American Association of State Highway Officials |oclc = 3332302 }}</ref> The ''[[Manual on Uniform Traffic Control Devices]]'' (MUTCD) standards revised the shield in the 1961,<ref name="MUTDC61">{{cite book |author1 = National Joint Committee on Uniform Traffic Control Devices |author2 = American Association of State Highway Officials |year = 1961 |chapter = Part&nbsp;1: Signs |chapter-url = http://www.trafficsign.us/oldmutcd/1961/1-signs.pdf |title = Manual on Uniform Traffic Control Devices for Streets and Highways |edition = 1961 |location = Washington, DC |publisher = Bureau of Public Roads |pages = 79–80 |oclc = 35841771 |access-date = February 22, 2012 |archive-date = April 14, 2012 |archive-url = https://web.archive.org/web/20120414190819/http://www.trafficsign.us/oldmutcd/1961/1-signs.pdf |url-status = live }}</ref> 1971,<ref name="MUTDC71">{{cite book |author1 = National Joint Committee on Uniform Traffic Control Devices |author2 = American Association of State Highway Officials |year = 1971 |chapter = Chapter&nbsp; 2D. Guide Signs: Conventional Roads |chapter-url = http://www.trafficsign.us/oldmutcd/1971/2d-guidesignsconv.pdf |title = Manual on Uniform Traffic Control Devices for Streets and Highways |edition = 1971 |location = Washington, DC |publisher = Federal Highway Administration |page = 88 |oclc = 221570 |access-date = February 22, 2012 |archive-date = November 29, 2011 |archive-url = https://web.archive.org/web/20111129185358/http://trafficsign.us/oldmutcd/1971/2d-guidesignsconv.pdf |url-status = live }}</ref> and 1978<ref name="MUTDC78">{{cite book |author = National Advisory Committee on Uniform Traffic Control Devices |year = 1978 |chapter = Chapter&nbsp; 2D. Guide Signs: Conventional Roads |chapter-url = http://www.trafficsign.us/oldmutcd/1978/2d-guidesigns.pdf |title = Manual on Uniform Traffic Control Devices for Streets and Highways |edition = 1978 |location = Washington, DC |publisher = Federal Highway Administration |page = ((2D-5)) |oclc = 23043094 |access-date = February 22, 2012 |archive-date = November 29, 2011 |archive-url = https://web.archive.org/web/20111129165921/http://trafficsign.us/oldmutcd/1978/2d-guidesigns.pdf |url-status = live }}</ref> editions.

===Exit numbering===
{{more citations needed section|date=June 2011}}
The majority of Interstates have [[exit number]]s. Like other highways, Interstates feature [[Road signs in the United States#Guide signs|guide signs]] that list [[control cities]] to help direct drivers through interchanges and exits toward their desired destination. All [[Road signs in the United States|traffic sign]]s and [[lane]] markings on the Interstates are supposed to be designed in compliance with the [[Manual on Uniform Traffic Control Devices]] (MUTCD). There are, however, many local and regional variations in signage.

For many years, California was the only state that did not use an exit numbering system. It was granted an exemption in the 1950s due to having an already largely completed and signed highway system; placing exit number signage across the state was deemed too expensive. To control costs, California began to incorporate exit numbers on its freeways in 2002—Interstate, US, and state routes alike. [[California Department of Transportation|Caltrans]] commonly installs exit number signage only when a freeway or interchange is built, reconstructed, retrofitted, or repaired, and it is usually tacked onto the top-right corner of an already existing sign. Newer signs along the freeways follow this practice as well. Most exits along California's Interstates now have exit number signage, particularly in rural areas. California, however, still does not use mileposts, although a few exist for experiments or for special purposes.<ref>{{cite web |first = Daniel P. |last = Faigin |date = December 29, 2015 |url = http://www.cahighways.org/num-postmiles.html |work = California Highways |title = Numbering Conventions: Post Miles |access-date = March 15, 2017 |archive-url = https://web.archive.org/web/20170131190248/http://www.cahighways.org/num-postmiles.html |archive-date = January 31, 2017 |url-status = live }}{{self-published source|date=March 2017}}</ref>{{self-published inline|certain=y|date=March 2017}} 

In 2010–2011, the [[Illinois State Toll Highway Authority]] posted all new mile markers to be uniform with the rest of the state on I‑90 (Jane Addams Memorial/Northwest Tollway) and the I‑94 section of the Tri‑State Tollway, which previously had matched the I‑294 section starting in the south at I‑80/I‑94/IL Route 394. This also applied to the tolled portion of the Ronald Reagan Tollway (I-88). The tollway also added exit number tabs to the exits.{{citation needed|date=December 2010}}

Exit numbers correspond to Interstate mileage markers in most states. On [[Interstate 19|I‑19]] in [[Arizona]], however, length is measured in kilometers instead of miles because, at the time of construction, [[Metrication in the United States|a push for the United States to change]] to a [[metric system]] of measurement had gained enough traction that it was mistakenly assumed that all highway measurements would eventually be changed to metric (and some distance signs retain metric distances);<ref>{{cite web |last1 = Zhang |first1 = Sarah |date = October 7, 2014 |title = An Arizona Highway Has Used the Metric System Since the 80s |url = https://gizmodo.com/an-arizona-highway-has-used-the-metric-system-since-the-1643536691 |website = Gizmodo |access-date = February 25, 2019 |archive-url = https://web.archive.org/web/20190225103128/https://gizmodo.com/an-arizona-highway-has-used-the-metric-system-since-the-1643536691 |archive-date = February 25, 2019 |url-status = live}}</ref> proximity to metric-using Mexico may also have been a factor, as I‑19 indirectly connects I‑10 to the [[Mexican Federal Highway]] system via surface streets in [[Nogales, Arizona|Nogales]]. Mileage count increases from west to east on most even-numbered Interstates; on odd-numbered Interstates mileage count increases from south to north.

Some highways, including the [[New York State Thruway]], use sequential exit-numbering schemes. Exits on the New York State Thruway count up from [[Yonkers, New York|Yonkers]] traveling north, and then west from Albany. I‑87 in New York State is numbered in three sections. The first section makes up the [[Major Deegan Expressway]] in [[the Bronx]], with interchanges numbered sequentially from 1 to 14. The second section of I‑87 is a part of the [[New York State Thruway]] that starts in Yonkers (exit&nbsp;1) and continues north to Albany (exit&nbsp;24); at Albany, the Thruway turns west and becomes I‑90 for exits&nbsp;25 to 61. From Albany north to the Canadian border, the exits on I‑87 are numbered sequentially from 1 to 44 along the [[Adirondack Northway]]. This often leads to confusion as there is more than one exit on I‑87 with the same number. For example, exit&nbsp;4 on Thruway section of I‑87 connects with the Cross County Parkway in Yonkers, but exit&nbsp;4 on the Northway is the exit for the Albany airport. These two exits share a number but are located {{convert|150|mi}} apart.

Many northeastern states label exit numbers sequentially, regardless of how many miles have passed between exits. States in which Interstate exits are still numbered sequentially are Connecticut, Delaware, New Hampshire, New York, and Vermont; as such, three of the main Interstate Highways that remain completely within these states ([[Interstate 87 (New York)|87]], [[Interstate 88 (New York)|88]], [[Interstate 89|89]]) have interchanges numbered sequentially along their entire routes. Maine, Massachusetts, Pennsylvania, Virginia, Georgia, and Florida followed this system for a number of years, but have since converted to mileage-based exit numbers. Georgia renumbered in 2000, while Maine did so in 2004. Massachusetts converted its exit numbers in 2021, and most recently Rhode Island in 2022.<ref>{{cite web |author = Massachusetts Department of Transportation |date = n.d. |title = Massachusetts Department of Transportation completed projects |url = https://www.mass.gov/info-details/massachusetts-department-of-transportation-completed-projects#statewide-exit-renumbering-project---2021- |publisher = Massachusetts Department of Transportation |access-date = September 20, 2022 }}</ref> The [[Pennsylvania Turnpike]] uses both mile marker numbers and sequential numbers. Mile marker numbers are used for signage, while sequential numbers are used for numbering interchanges internally. The [[New Jersey Turnpike]], including the portions that are signed as I‑95 and I‑78, also has sequential numbering, but other Interstates within New Jersey use mile markers.

===Sign locations===
There are four common signage methods on Interstates:
* Locating a sign on the ground to the side of the highway, mostly the right, and is used to denote exits, as well as [[rest area]]s, motorist services such as gas and lodging, recreational sites, and freeway names
* Attaching the sign to an overpass
* Mounting on full [[gantry (road sign)|gantries]] that bridge the entire width of the highway and often show two or more signs
* Mounting on half-gantries that are located on one side of the highway, like a ground-mounted sign