About Impact Recovery Systems

Order Our Catalog

GSA Contract Holder # GS-03-002CA

Click Here to view and download our newsletter archives.

Determining Where Hazard Markers are Needed

Hazard markers play a vital role in safeguarding motorists by deterring them from dangerous sections of public roads.  Knowing where they should be placed is crucial for their proper use.  This article will provide a summary view of the topic for introductory purposes. 


T-Intersection Sight Boards

These are used to notify motorists that the road they’re on will abruptly terminate at an intersection with another road, which runs at a 90 degree angle to the one currently occupied.  Sight boards are used to supplement standard measures such as stop signs and lights, so that drivers don’t overshoot the intersection.  See illustration below.

T-Intersection Sight Boards diagram

 Bi-directional Hazard Markers

These are used to alert motorists to upcoming road obstructions and to advise them to drive around them.  Arrows pointing both to the left and right indicate drivers can go in either direction to avoid the hazard.


For example, say that an island is placed so that it divides the road ahead.  A bi-directional marker would advise motorists of this and direct them to drive to the left or right to avoid it.

Bi-directional Hazard Markers diagram

Unidirectional Hazard Marker


These hazard markers serve the same purpose as bi-directional markers, except that motorists are advised to go in only one direction to avoid the upcoming hazard.  They’re used when the road ahead narrows or is partially obstructed.

Unidirectional Hazard Marker diagram

Obstruction Markers

These are used to notify drivers that an object or hazard, which requires them to stop traveling in their current direction, is ahead.  Such objects or hazards might take the form of construction, flooded streets, degraded road conditions, or physical objects.

Obstruction Markers diagram



Situations that Require the Use of Hazard Markers

The overall purpose of hazard markers is to notify drivers of potential dangers ahead of them, so that they will not be caught unawares.  The term “potential dangers” encompasses a broad array of possible impediments to travel.  Here are some specific situations in which hazard markers might be used.

  • In cases where the road ahead is flooded or covered with ice.
  • In cases where the road surface ahead has deteriorated to a dangerous point, either due to normal wear or tear or to damage caused by a natural or human-caused event.
  • In cases where road construction or maintenance is being performed up ahead.
  • In cases where a bridge ahead has collapsed or is unsafe to use.
  • In cases where permanent structural elements require an extra degree of vigilance on the part so motorists.  Examples include islands, one-lane bridges, bridge piers, manhole covers, raised or lowered road surface, recent changes to the shape or contour of the road, and spots where the road narrows.
  • In cases where sharp curves are coming up, and/or the road shoulder narrows or disappears. 


The exact forms hazard markers take vary depending on the locality where they are being used.  For example, in the United States, markers often differ significantly in appearance from those used in European nations.  Whatever their form, it is essential to be aware of and abide by all hazard markers, as they could prevent an accident or serious injury.  Additionally, the use hazard markers by safety officials is a must once a hazard or construction zone has been established.