Editing Speed limit (section)

=== Variable speed limits ===
[[File:Variable speed limit.jpg|thumb|upright|Example variable speed limit sign in the United States, in mph]]
[[File:Digital speed limit sign.jpeg|thumbnail|upright|Digital speed limit sign for variable speed limits]]
In Germany, the first known experiments with variable speed limit signs took place in 1965 on a {{convert|30|km|adj=on}} stretch of German motorway, the [[Bundesautobahn 8|A8]] between [[Munich]] and the border city of [[Salzburg]], Austria. Mechanically variable message signs could display speeds of 60, 80 and 100&nbsp;km/h, as well as text indicating a "danger zone" or "accident". Personnel monitored traffic using video technology and manually controlled the signage.<ref>{{citation|url=http://elib.uni-stuttgart.de/opus/volltexte/2003/1468/pdf/Dissertation_Schick.pdf|title=(translation) "Influence of Traffic Control Systems on Freeway Capacity and Stability of Traffic Flow"; Original Title "Einfluss von Streckenbeeinflussungsanlagen auf de Kapazitaet von Autobahnabschnitten sowie die Stabilitaet des Verkehrsflusses"|publisher=[[University of Stuttgart]]|date=June 2003|author=Peter Schick|access-date=2010-10-16|page=20|doi=10.18419/opus-175|isbn=9783980821841|quote=(translation) "The first experiment was carried out in 1965 on a 30 km section of the A8 from Salzburg to Munich. The system consisted of mechanically variable message signs at a distance of 2 km, which could display speeds of 60, 80 and 100 km/h, and "danger zone" and "accident." Personnel monitored traffic using video technology and manually controlled the signage. Studies reported a decrease in traffic disruptions and breakdowns, harmonization of the velocity distribution and an increase in performance (Zackor 1972, see also Chapter 3.2.2)." German text: "Die erste linienhafte Beeinflussung des Verkehrs erfolgte im Jahr 1965 durch die Errichtung einer Wechselverkehrszeichenanlage auf einem 30 km langen Abschnitt der A8 auf der Richtungsfahrbahn Salzburg – München. Die Anlage bestand aus neben der Fahrbahn angebrachten mechanischen Wechselverkehrszeichen im Abstand von 2 km, die StVO-gerechte Zeichen für die Geschwindigkeitsbegrenzungen 60, 80 und 100 km/h sowie "Gefahrstelle" und "Unfall" anzeigen konnten (Abb. 2-1). Diese Zeichen wurden vom Betreiberpersonal, das mittels Videotechnologie eine Übersicht über das Verkehrsgeschehen hatte, manuell geschaltet. Somit konnte erstmals auf einer Autobahn die Geschwindigkeit des Verkehrs beeinflusst sowie eine Unfallwarnung vorgenommen werden. Die ersten Erfahrungen und wissenschaftlichen Untersuchungen berichten von einer Abnahme der Störungen und Verkehrszusammenbrüche, einer Harmonisierung der Geschwindigkeitsverteilung sowie einer Steigerung der Leistungsfähigkeit (ZACKOR 1972, siehe auch Kapitel 3.2.2).}}</ref> Beginning in the 1970s, additional advanced traffic control systems were put into service. Modern motorway control systems can work without human intervention using various types of sensors to measure traffic flow and weather conditions. In 2009, {{convert|1300|km}} of German motorways were equipped with such systems.<ref>{{citation|author=Ralf Schmahld|title=(translation) "20 years waiting in traffic jams"; Original Title "20 Jahre im Stau gestanden"|date=2009-08-06|url=http://www.turus.net/reise/4297-20-jahre-im-stau-gestanden.html?fontstyle=f-larger|publisher=Reise (Travel) magazine|quote=(translation) "A total of 1,300 kilometers of motorways now have traffic control systems for the harmonization of the traffic flow by speed limits and traffic warning, and the government expects to expand their use: 2500 km stretch of motorway could be controlled by these dynamic control systems." German text: "An insgesamt 1.300 Kilometern der Bundesautobahnen seien inzwischen Streckenbeeinflussungsanlagen zur Harmonisierung des Verkehrsablaufs durch Geschwindigkeitsbeschränkungen und Gefahrenwarnung installiert worden, teilt die Regierung weiter mit. 2.500 Kilometer Autobahnstrecke könnten mittels dynamischer Netzbeeinflussungsanlagen gesteuert werden"|access-date=2010-10-16}}</ref>

In the United States, heavily traveled portions of the [[New Jersey Turnpike]] began using variable speed limit signs in combination with [[variable message signs]] in the late 1960s. Officials can adjust the speed limit according to weather, traffic conditions, and construction.<ref>{{citation|url=http://ntl.bts.gov/lib/jpodocs/briefing/12164.pdf|title=Examples of Variable Speed Limit Applications. Speed Management Workshop|date=2000-01-09|publisher=[[Transportation Research Board]]. 79th Annual Meeting|author=Mark Robinson|access-date=2010-10-17|quote="New Jersey. Status: Active (installed in the late 1960s). Objective: to provide early warning to motorists of slow traffic or hazardous road conditions. Setting: Urban/Rural - New Jersey Turnpike.|archive-date=2011-09-27|archive-url=https://web.archive.org/web/20110927115419/http://ntl.bts.gov/lib/jpodocs/briefing/12164.pdf|url-status=dead}}</ref> More typically, variable speed limits are used on remote stretches of highway in the United States in areas with extreme changes in driving conditions.<ref name="ntl.bts.gov">{{cite web|url=https://ntl.bts.gov/repository-notice|title=Repository Notice - Bureau of Transportation Statistics|website=ntl.bts.gov|access-date=2019-01-01|archive-date=2019-01-02|archive-url=https://web.archive.org/web/20190102231239/https://ntl.bts.gov/repository-notice|url-status=dead}}</ref> For example, variable limits were introduced in October 2010 on a {{convert|52|mi|adj=on}} stretch of [[Interstate 80]] in [[Wyoming]], replacing the winter season speed reduction from {{cvt|75|to|65|mph}} that had been in place since 2008.<ref>{{cite web|url=http://www.ksl.com/?nid=148&sid=4399274|title=WYDOT proposes to lower I-80 speed limit|date=2008-09-29|quote=The Wyoming Department of Transportation says it plans to impose a speed limit of {{cvt|65|mph}} on a {{cvt|52|mi}} stretch of the interstate between Laramie and Rawlins. The reduction from the existing speed limit of {{cvt|75|mph}} will take effect Oct. 15 and continue for six months. Also, WYDOT intends to install variable speed-limit signs on the same stretch of highway so the limit can be lowered further because of bad weather. The section is between the Quealy Dome Interchange, {{cvt|20|mi}} west of Laramie, and the Peterson Interchange, {{cvt|22|mi}} east of Rawlins, the agency said.|publisher=[[KSL-TV]]|access-date=2010-10-16}}</ref><ref>{{cite web|url=http://www.landlinemag.com/todays_news/Daily/2010/Oct10/101110/101510-04.htm|title=Wyoming seasonal speed limit will vary with conditions|date=2010-10-15|quote=""When it’s all horizontal and drifts, it kills the visibility, and we have a horrible time trying to keep people on the road," Wyoming DOT engineer Tim McGary told Land Line Now on Sirius XM. McGary says this winter, truckers on I-80 will no longer see that {{cvt|65|mph}} seasonal speed limit between Laramie and Rawlins. Instead, the whole {{cvt|52|mi|adj=on}} stretch will have the electronic, variable speed limit signs that the DOT started installing last year. The variable signs allow the DOT to lower or raise the speed limit in {{cvt|5|mph}} increments depending on the weather conditions. And McGary says they work. The statistics are kind of showing that if we’re on top of things with our plow operators and troopers out there, and we get the speed limits reduced appropriately to the weather conditions, people are complying pretty well with that," McGary said. "Our crash rates have gone down, and we’re hoping to continue that trend.""|publisher=[[Land Line Magazine]]|access-date=2010-10-16|archive-date=2010-12-08|archive-url=https://web.archive.org/web/20101208192323/http://www.landlinemag.com/todays_news/Daily/2010/Oct10/101110/101510-04.htm|url-status=dead}}</ref> This Variable Speed Limit system has been proven effective in terms of reducing crash frequency and road closures.<ref>{{cite conference|author1=Saha, P.|author2=Young, R.|date=2014-08-01|title=Weather-Based Safety Analysis for the Effectiveness of Rural Variable Speed Limit (VSL) Corridors|conference=Transportation Research Board 93rd Annual Meeting|id=No. 14-2293|url=http://docs.trb.org/prp/15-1916.pdf|url-status=dead|archive-date=2015-02-23|archive-url=https://web.archive.org/web/20150223185553/http://docs.trb.org/prp/15-1916.pdf}}</ref><ref>{{cite report|author1=R. Young|author2=V. Sabawat|author3=P. Saha|author4=Y. Sui|date=2012-05-01|title=Rural Variable Speed Limits: Phase II|id=FHWA-WY-13/03F|url=https://rosap.ntl.bts.gov/view/dot/29333|access-date=2022-04-10}}<br />{{cite report|title=Final Report: FHWA-WY-13/03F|date=May 2013|url=http://www.dot.state.wy.us/files/live/sites/wydot/files/shared/Planning/Research/RS04210.pdf|archive-url=https://web.archive.org/web/20150522110130/http://www.dot.state.wy.us/files/live/sites/wydot/files/shared/Planning/Research/RS04210.pdf|archive-date=2015-05-22|url-status=dead|access-date=2022-04-11}}</ref> Similarly, [[Interstate 90]] at [[Snoqualmie Pass]] and other mountain passes in Washington State have variable speed limits as to slow traffic in severe winter weather.<ref name="ntl.bts.gov" /><ref>{{cite web|url=http://www.tfhrc.gov/pubrds/03jan/10.htm|title=Managing Speed|date=January–February 2003|work=Public Roads|publisher=www.tfhrc.gov|access-date=2008-07-06|archive-date=2008-09-21|archive-url=https://web.archive.org/web/20080921132642/http://www.tfhrc.gov/pubrds/03jan/10.htm|url-status=dead}}</ref> As a response to fog-induced chain-reaction collisions involving 99 vehicles in 1990, a variable speed limit system covering {{convert|19|mi}} of [[Interstate 75]] in [[Tennessee]] was implemented in fog-prone areas around the [[Hiwassee River]].<ref>{{cite web|url=https://ops.fhwa.dot.gov/weather/best_practices/casestudies/022.pdf|title=Tennessee Low Visibility Warning System|publisher=Federal Highway Administration|access-date=2010-10-17}}</ref> The [[Georgia Department of Transportation]] installed variable speed limits on part of [[Interstate 285 (Georgia)|Interstate 285]] around [[Atlanta]] in 2014. These speeds can be as low as {{cvt|35|mph}} but are generally set to {{cvt|35|mph}}.<ref>{{cite news|url=http://atlantaforward.blog.ajc.com/2014/09/29/moving-speed-limits-on-i-285/|title=Moving speed limits on I-285|date=2014-09-29|work=[[Atlanta Journal-Constitution]]|access-date=2015-08-22}}</ref> In 2016, the [[Oregon Department of Transportation]] installed a variable speed zone on a {{cvt|30|mi|adj=on}} stretch of [[Interstate 84 in Oregon|Interstate 84]] between [[Baker City, Oregon|Baker City]] and Ladd Canyon. The new electronic signs collect data regarding temperature, skid resistance, and average motorist speed to determine the most effective speed limit for the area before presenting the limit on the sign. This speed zone was scheduled to be activated November 2016.{{citation needed|date=January 2017}} [[Ohio]] established variable speed limits on three highways in 2017, then in 2019 granted the authority to the [[Ohio Department of Transportation]] to establish variable limits on any of its highways.<ref>{{orc|45|11|21}}(H)(3)</ref><ref>{{cite news|url=https://www.news-herald.com/news/odot-variable-speed-limits-only-used-to-improve-safety/article_5c4fcf5e-57b6-11e9-b3fb-135dccc9e4ac.html|title=ODOT: Variable speed limits only used to improve safety|last=Felton|first=Chad|date=2019-04-05|work=[[The News-Herald (Ohio)|The News-Herald]]|access-date=2019-04-06|location=Willoughby, OH}}</ref>

In the United Kingdom, a variable speed limit was introduced on part of the [[M25 motorway]] in 1995, on the busiest {{convert|14|mi|adj=on}} section from junction 10 to 16. Initial results suggested savings in journey times, smoother-flowing traffic, and a decrease in the number of crashes; the scheme was made permanent in 1997.<ref>{{citation|url=http://www.nao.org.uk/publications/nao_reports/04-05/040515.pdf|title=Report (HC 15, 2004-05): Tackling congestion by making better use of England's motorways and trunk roads (Full Report)|publisher=[[National Audit Office (United Kingdom)|National Audit Office]]|date=2004-11-26|access-date=2009-09-17|page=21|quote=The initial results of the one year trial of Variable Speed Limits indicated savings in journey times, smoother flowing traffic and a fall in the number of accidents. Based on these findings, the Agency converted the trial into a permanent facility in 1997. Variable Speed Limits have generally been popular with road users who have reported perceived benefits, including less congestion and less stressful journeys. The Agency could not prove a business case to use the measure elsewhere. Conditions at the site of the Variable Speed Limits trial were not stable before or during the trial, or in the period of extended monitoring that followed it. Traffic volumes changed and the Agency introduced new technology and new lighting and widened the motorway at both ends of the trial site, preventing it from establishing properly controlled and reliable "before and after" data to assess the measure’s impact. Without reliable data, the Agency could not prove a business case to use the measure elsewhere. As a result, in 2002 the Agency extended the Variable Speed Limits trial, at a further budgeted cost of £3.9 million, to cover an additional eight kilometres of the M25, where conditions were expected to be more stable, in order to collect sufficient before and after data to prepare a business case.|archive-date=2008-10-30|archive-url=https://web.archive.org/web/20081030122101/http://www.nao.org.uk/publications/nao_reports/04-05/040515.pdf|url-status=dead}}</ref> However, a 2004 National Audit Organisation report noted that the business case was unproved; conditions at the site of the Variable Speed Limits trial were not stable before or during the trial, and the study was deemed neither properly controlled nor reliable. Since December 2008 the [[M1 motorway#Widening from Junction 6a to 10|upgraded section of the M1]] between the M25 and [[Luton]] has had the capability for variable speed limits.<ref>{{cite web|url=http://www.highways.gov.uk/roads/documents/M1_Official_Completion_Ceremony.pdf|title=M1 Junctions 6A to 10 Official Completion Ceremony|publisher=Highways Agency|url-status=dead|archive-url=https://web.archive.org/web/20091115063727/http://www.highways.gov.uk/roads/documents/M1_Official_Completion_Ceremony.pdf|archive-date=2009-11-15}}</ref> In January 2010 temporary variable speed cameras on the M1 between J25 and J28 were made permanent.<ref>{{cite news|title=M1 works speed cameras will stay|work=BBC News|date=2010-01-03|url=http://news.bbc.co.uk/1/hi/england/nottinghamshire/8438375.stm|access-date=2010-04-13}}</ref>

New Zealand introduced variable speed limits in February 2001. The first installation was on the [[Ngauranga Gorge]] section of the dual carriageway on [[State Highway 1 (New Zealand)|State Highway 1]], characterized by steep terrain, numerous bends, high traffic volumes, and a higher than average accident rate. The speed limit is normally {{cvt|80|kph}}.<ref>{{cite web|url=http://www.ipenz.org.nz/ipenztg/papers/2002_pdf/31_Fergus_Turner.PDF|title=Monitoring Incident and Travel Behaviour Through the Use of ATMS Architecture|date=22–25 September 2002|quote=initial results of a Transfund Research project being undertaken to evaluate the effectiveness of Variable Message Speed Signs (VMSS) within the Ngauranga Active Traffic Management System (NATMS). NATMS is an incident based system whose objective is to facilitate the passage of traffic through a very demanding section of state highway just north of Wellington... A unique feature of the NATMS is the use of VMSS which display a mandatory speed imposed by controllers in response to an incident or prevailing traffic conditions... In February 2001 Transit New Zealand (TNZ) commissioned the operation of the Ngauranga Active Traffic Management System (NATMS) on State Highway 1, north of Wellington, New Zealand. The NATMS covers a 4 km stretch of State Highway between Johnsonville and the SH1 / SH2 Interchange. The NATMS is the first system in New Zealand to use Automatic Incident Detection (AID) and was chosen because of the challenging driving conditions which are compounded by steep terrain, numerous bends and a high degree of weaving between lanes. This, in conjunction with a volume over 60,000 vehicles per day and an accident rate higher than the national average were contributing factors in the introduction of the NATMS.|author=Andrew W Fergus and David J Turner (MWH NZ Ltd.)|access-date=2010-10-21|url-status=dead|archive-url=https://web.archive.org/web/20100805191744/http://www.ipenz.org.nz/ipenztg/papers/2002_pdf/31_Fergus_Turner.PDF|archive-date=2010-08-05}}</ref>

[[Austria]] undertook a short-term experiment in 2006, with a variable limit configuration that could increase statutory limits under the most favorable conditions, as well as reduce them. In June 2006, a stretch of motorway was configured with variable speed limits that could increase the general Austrian motorway limit of {{cvt|130|to|160|kph}}.<ref>{{cite web|url=http://oesterreich.orf.at/kaernten/stories/114065/|title=German: Ein Monat 'Tempo 160' auf der A10. English: A month of 'Tempo 160' on the A10|quote="German: Den 'Tempo 160-Test' auf der A10 bezeichnete Gorbach "allen Unkenrufen zum Trotz" als 'Meilenstein in der europäischen Verkehrspolitik'. Er betonte im Rahmen einer Pressekonferenz in Wien, dass mit Tempo 160 'nicht die Raser gefördert, sondern die Geschwindigkeit flexibilisiert' werden soll. English: '[The then Austrian Minister for Transportation Hubert] Gorbach said the 'Test Speed 160' on the A10 [motorway] was 'a milestone in European transport policy-despite all predictions to the contrary.' He said at a press conference in Vienna that a 160 limit 'does not promote speeding, but more flexible travel speeds'.|access-date=2010-04-16|archive-date=2011-07-18|archive-url=https://web.archive.org/web/20110718111933/http://oesterreich.orf.at/kaernten/stories/114065/|url-status=dead}}</ref> Then Austrian Transport Minister [[Hubert Gorbach]] called the experiment "a milestone in European transport policy-despite all predictions to the contrary"; however, the experiment was discontinued.{{Citation needed|date=June 2019}}