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Shared Characteristics of Highway Safety Equipment Signage

Most highway safety equipment, including signage, is designed to work in virtually any environment, from densely packed urban areas to wide open rural settings.  This post will examine the common design principles that guide sign manufacturers.  The information in this article is derived from this publication.

Common Design Principles

All public signs fall into one of three classes:

  1. Regulatory signs.  These products communicate the rules of the road to drivers.  Examples include STOP and YIELD signs, as well as speed limit notices.  Because of their singular importance, highway crews must ensure these signs are always in good repair and in place.  Workers should replace damaged or stolen signs as soon as possible.
  2. Warning signs.  These products give drivers timely warning of approaching hazardous conditions.  Possible situations that may call for their placement include twisting or highly curved roads, low shoulders, damage to the road surface from accidents or inclement weather, and the presence of pedestrian or animal crosswalks. For example, many rural areas display cattle crossing signs in locations where ranchers routinely move their herd across public roads.  Sometimes these signs are temporary, other times permanent.
  3. Guide signs.  These products help drivers to navigate their way to a desired destination.  Some of the information these signs convey includes directions, preferred routes, points of interest, cultural information, and the presence of services like gas stations and lodging.  While its primary purpose is informative, this signage also helps to prevent driver distraction, contributing to overall public safety and well-being.

Work Zone Signs
A special class of highway safety equipment signage is concerned with preventing accidents around road construction and road maintenance crews.  These signs are generally intended for temporary use only.  They may convey messages like ROAD WORK AHEAD or DETOUR.  It’s important for road crews to ensure these signs are in place and in good working order at all times, as their absence could quickly lead to disastrous results.
The Role of Retroreflectivity in Highway Safety Equipment
Motorists operate their vehicles in all kinds of conditions, from bright summer days to dark, dismal winter nights.  It’s imperative that they be able to see road signs clearly in all types of conditions.  One of the features manufacturers use to ensure this function is retroreflectivity.  This refers to the installation of highly reflective materials (such as glass beads) within sign sheeting.  Sheeting types range in classification from type 1 to type 11.
The Role of Sign Supports in Maintaining Highway Safety Equipment
Any sign is only as good as the medium that supports it.  In most cases, this means a sturdy steel or wood post sunk into the surrounding earth and held in place by concrete or asphalt.   When properly installed, these supports can last many years without significant degradation.
While it may seem counterintuitive, however, it is possible for sign supports to be too strong.  This is because safety engineers are concerned not only about sign integrity but with protecting errant motorists who may strike the sign with their vehicle.  For this reason, modern sign supports are designed with breakaway features.  For example, installers may drill holes near the base of a wooden sign post to weaken it slightly.  More commonly, however, road crews use U-channel steel for sign supports, as this metal offers excellent resistance to the elements yet gives easily if struck by a vehicle.
Modern society could not operate without the presence of highway safety equipment, including the types of signs discussed in this article.  To derive full value from its use, however, signage must be designed, installed, and maintained in accord with sound engineering principles.