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Roadway Operations & Maintenance > Work Zone Management > Variable Speed Limits


Variable speed limit systems use sensors to monitor working conditions, traffic and/or weather conditions within work zones, posting appropriate enforceable speed limits on dynamic message signs.


Portable variable speed limit system in Utah successfully reduces speed limit by 15 to 25 mi/hr near work zones.(January 7 - 11, 2018)

As a result of a Portable Variable Speed Limit System installed along a construction zone in Alaska, the percentage of vehicles speeding decreased by 57 percent.(10/06/2017)

In Smart Zone work zones, 71 percent of local resident survey respondents found variable speed limit signs useful.(January 28, 2015)

Variable advisory speed limit systems reduce variability in speeds and improve safety at congested work zones.(08/01/2013)

A variable speed limit system used to regulate traffic flow through work zones on a 7.5 mile section of I-495 saved motorists approximately 267 vehicle-hours of delay each day.(03/01/2010)

Field data collected over the last two decades show variable speed limit (VSL) systems can reduce crash potential by 8 to 30 percent. (03/01/2010)

A variable speed limit system deployed at a work zone on I-96 in Lansing, Michigan contributed to a decrease in the number of high-speed vehicles in the work zone.(September 2003)

A variable speed limit system deployed at a work zone on I-96 in Lansing, Michigan contributed to a decrease in travel times and an increase in average speeds.(September 2003)

On the Køge Bugt Motorway in Copenhagen, Denmark, variable speed limits reduced vehicle speeds by up to 5 km/h and contributed to smoother traffic flow during peak periods.(8 April 2003)

A survey of motorists in Copenhagen, Denmark, found that 80 percent of respondents were satisfied with variable speed limits and the traveler information posted on dynamic message signs.(8 April 2003)

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