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August 9, 2023

How Speed Signs Increase Road Safety

According to Federal Highway Administration (FHWA) statisticsspeed is a contributing factor in over 30% of fatal work zone crashes. Reducing speeds entering and through the work zone is one of the key strategies to reduce incidents and fatalities of motorists and workers in work zones. The use of Work Zone Digital Speed Limit Signs (VSL) and the combination of Digital Speed Limit with Speed Feedback displays have proven to slow motorists’ speeds in work zones.

The FHWA’s Proven Safety Countermeasures section has recently published a study stating how VSLs can reduce crashes on freeways up to:

  • 34% for total crashes
  • 65% for rear-end crashes
  • 51% for fatal and injury crashes

The Work Zone Digital Speed Limit Sign (WZDSL) has been extremely effective in several states to reduce speeds “When Workers Are Present”. The two, 18” white LED speed display mounted to a MUTCD speed limit sign combined with two, 12” flashing beacons reduced speeds by up to 14 MPH (22.5 KM /H) when combined with presence lights on work zones at night, according to studies conducted independently by North Carolina DOT and Purdue University. When Workers Are Present, the two-digit speed limit will be reduced to the work zone speed limit and the two flashing beacons will be activated. When workers are not present, the two-digit display will display the posted speed limit.


The Speed Wizard combines a Work Zone Digital Speed Limit Sign and Speed Feedback Sign to lower speeds immediately before reaching workers. The same two-digit display with speed limit sign is coupled with a full-matrix display speed feedback sign. The full-matrix display can display two-digit speed and Slow Down messages to provide multiple levels of warning and achieve greater speed compliance. By notifying motorists of work zone speed and excessive motorist speed, the Speed Wizard provides smoother traffic flow and helps reduce rear-end collisions.

Speed Wizard

Both the WZDSL and Speed Wizard can push real-time work zone speed limits to Waze and the Work Zone Data Exchange (WZDx) to give motorists and DOTs real-time speed limit information, further contributing to road safety.