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Why Hazard Markers for Open-Grate Bridges?

The importance of hazard markers for open-grate bridges was made apparent by an incident that occurred in Seattle in 2007.  A bicycle rider named Mickey Gendler was riding across a grated bridge when he attempted to turn left.  His front wheel became caught in a gap between the metal grates, causing him to flip over his handlebars and crush his helmet.  The damage to his brain and nervous system left Gendler without the use of any of his limbs.


Three years later, in 2010, the state agreed to pay Gendler $8 million in settlement claims against the Washington DOT.  An investigation turned up the fact that the bridge had caused prior bike accidents, due to the spacing of its grates.  While the DOT was aware of these incidents, it made no attempt to fix the problem until the threat of a lawsuit forced it to act.


This heart-breaking accident might have been prevented if the bridge had the appropriate hazard markers.  As it is, the event points out the dangers inherent in open-grate bridges, and the urgency of taking steps to ensure the safety of both cyclists and pedestrians who use them.


What are Open-Grate Bridges?

In the years immediately following WWII, the U.S. was a busy place.  Economic expansion occurred so fast that government struggled to build the infrastructure needed to keep up with the increasing number of vehicles on the road.  The problem was especially vexing since many of the bridges in existence at the time were floored with wooden planks.  They were never designed to support the massive amounts of vehicular traffic the booming economy created.


At the time, steel was relatively cheap, so highways began to use grated steel for bridge surfaces.  At the time, it made good sense.  Grating offered several advantages, including the following:

  • It was lighter than other materials, meaning it could be added onto existing bridge frames that could never have supported heavier products like concrete.
  • Water couldn’t collect on its surface.  This makes grating immune to the cracking problems caused by ice freezing and thawing on road surfaces.
  • It was largely unaffected by wind, always a plus when building bridges for cars and trucks.  Bridges swaying in the wind are fine for foot traffic, but very bad for supporting multi-ton vehicles.


Steel-grated bridges popped up by the thousands coast-to-coast during the 1940s and 50s.  Hundreds are still being used across the country.  Unfortunately, time has revealed weaknesses in their design.  These include the following problems:

  • Road salt, commonly used for ice and snow control in northern states, eventually coats the grates, corroding the metal and weakening the original welds.  For this reason, many steel-grate bridges have been torn down and replaced with concrete structures in recent years.  Others are in need of regular repair or complete replacement of the grates.
  • Car tires never make full contact with the grating.  Because of this, there’s very little material to stop vehicles from skidding if the driver needs to brake.  This has led to countless accidents over the years.
  • Steel-grate bridges are unfriendly to both foot and bike traffic, as the incident in Seattle proves.  With millions of Americans choosing to walk or ride these days instead of driving, this fact presents significant hazards to a large part of the population.
  • Lane markings are difficult to see on open grate bridges due to the decreased surface available to mark.  This can be overcome by installing raised channelizing devices equipped with durable retro-reflectors.


Concrete or non-slip metal side paths have been installed on hundreds of the remaining open-grate bridges.  These are only a partial solution, however, as many cyclists and pedestrians are unaware of the dangers posed by using the grated surface.  For this reason, hazard markers serve a vital role as traffic safety systems.  They direct non-vehicular bridge users onto the side paths, protecting the public from harm and safeguarding government agencies from exposure to lawsuits.  Thus, hazard markers should be used on all open-grate bridges. Protect yourself.  Stop by our website and order your hazard markers today.