page_title: Speed limit
section_title: Variable speed limits
hierarchical_section_title: Speed limit / Regulations / Variable speed limits
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context_page_description: Road speed limits are used in most countries to set the legal maximum or minimum speed at which road vehicles may travel on a given stretch of road. Speed limits are generally indicated on a traffic sign reflecting the maximum or minimum permitted expressed as kilometres per hour and/or miles per hour. Speed limits are commonly set by the legislative bodies of national or provincial governments and enforced by national or regional police and judicial authorities. Speed limits may also be variable, or in some places unlimited, such as on most of the Autobahn in Germany.
  The first numeric speed limit for automobiles was the 10 mph limit introduced in the United Kingdom in 1861.
  The highest posted speed limit in the world is 160 km/h, which applies to two motorways in the UAE. Although speed limit and safety distance are poorly enforced in this country specifically on the Abu Dhabi to Dubai motorway resulting in dangerous traffic according to a French government travel advisory, while "drivers often drive at high speeds. Unsafe driving practices are common, especially on inter-city highways.
context_section_description: In Germany, the first known experiments with variable speed limit signs took place in 1965 on a 30 kilometer stretch of German motorway, the A8 between Munich and the border city of Salzburg, Austria. Mechanically variable message signs could display speeds of 60, 80 and 100 km/h, as well as text indicating a "danger zone" or "accident". Personnel monitored traffic using video technology and manually controlled the signage.  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, 1,300 kilometers (810 miles) of German motorways were equipped with such systems.
  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. More typically, variable speed limits are used on remote stretches of highway in the United States in areas with extreme changes in driving conditions. For example, variable limits were introduced in October 2010 on a 52-mile (84 km) stretch of Interstate 80 in Wyoming, replacing the winter season speed reduction from 75 to 65 mph (121 to 105 km/h) that had been in place since 2008. This Variable Speed Limit system has been proven effective in terms of reducing crash frequency and road closures.  Similarly, Interstate 90 at Snoqualmie Pass and other mountain passes in Washington State variable speed limits are used to slow traffic in severe winter weather.  As a response to fog-induced chain-reaction collisions involving 99 vehicles in 1990, a variable speed limit system covering 19 miles (31 km) of Interstate 75 in Tennessee was implemented in fog-prone areas around the Hiwassee River. The Georgia Department of Transportation installed variable speed limits on part of Interstate 285 around Atlanta in 2014. These speeds can be as low as 35 mph but are generally set to 65 mph. In 2016, the Oregon Department of Transportation installed a variable speed zone on a 30-mile stretch of Interstate 84 between 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. 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.
  In the United Kingdom, a variable speed limit was introduced on part of the M25 motorway in 1995, on the busiest 14-mile (23 km) 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.  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 upgraded section of the M1 between the M25 and Luton has had the capability for variable speed limits. In January 2010 temporary variable speed cameras on the M1 between J25 and J28 were made permanent.
  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, characterized by steep terrain, numerous bends, high traffic volumes, and a higher than average accident rate.  The speed limit is normally 80 km/h (50 mph).
  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 
caption: Digital speed limit sign for variable speed limits
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