Did You Know: Roadway Signing

Posted by on Jan 10, 2017

By Justin Watson, E.I., Infrastructure Designer

Roadway signing can directly affect the safety of the public by warning drivers and pedestrians of any number of roadway hazards, traffic maneuvers, navigation information, etc. Signing and/or resigning is one aspect of a safety project where the designer relays active information to the driver, whereas things such as shoulder rumble strips, striping, and raised pavement markers give passive information and feedback to the driver.

While working on Road Safety Audits (RSA) and other types of safety projects we are constantly evaluating the relay of information to the driver. Much of this is done with signage, and it is part of our job to ensure that it is done in the most efficient manner possible while commanding attention at known crash locations and trouble spots. For example, signing can be used to warn drivers of horizontal and vertical alignment changes, intersections, weather and pavement considerations, navigation, and school zones. But, it has to do so in a way that doesn’t inundate drivers with information or present too many decisions at one time for a driver. People can only process a certain amount of information at one time; signing needs to be limited so as not to overwhelm the driver or cause a distraction.

In addition to engineering judgment, there are standards and references that must be used to avoid these pitfalls. For our purposes at Sain Associates, the Manual on Uniform Traffic Control Devices for Streets and Highways 2009 Edition is the main reference along with Alabama Department of Transportation (ALDOT) or Tennessee Department of Transportation (TDOT) standards and specifications, depending on the location of the project. Other useful resources include the National Cooperative Highway Research Program: Human Factors Guidelines for Road Systems, Second Edition.

We’ve noticed that the industry has been trending toward a more psychological approach to signing.  At a training seminar I recently attended put on by Battelle, Center for Human Performance and Safety for ALDOT, we discussed the Human Factors Guidelines for Road Systems and focused specifically on the research and data collected on the behavioral trends of drivers and pedestrians.

This research includes data on things like:

  • Visual fixation of a driver’s eyes going through a horizontal curve or a busy urban street
  • Legibility of signs at varying distances, color recognition, and retro reflectivity
  • How the human eye perceives a horizontal and vertical curve in the roadway versus the actual geometry of the road
  • How the brain processes information more efficiently when it is presented in a symmetrical fashion (an example would be reading multiple exit signs on a busy freeway)

You may not have realized how much medical and psychological sciences influence the signs you see everyday as you drive your car. As research into the human brain continues, we are likely to see more advancements in engineering that will influence your daily commute.

2 Comments

  1. Gray Wells
    January 12, 2017

    Good work Justin! A current practice, which is both confusing and dangerous is the use of yield signs at traffic signals. There is no public information for which sign has the priority and which driver has the right of way. I think this should stop. Maybe a good topic for a new post.

    Reply
    • admin
      January 17, 2017

      Gray, we encounter this situation fairly often as well. In Section 2B.09 on page 53 of the Manual on Uniform Traffic Control Devices (MUTCD) 2009 Edition it states the following:

      “YIELD signs may be installed:
      …C. For a channelized turn lane that is separated from the adjacent travel lanes by an island, even if the
      adjacent lanes at the intersection are controlled by a highway traffic control signal or by a STOP sign.”

      I think the operative part of this condition is that it is needed when a channelized turn lane is separated from the adjacent travel lane. In a case like this, the driver may not be facing the signal head when performing the right turn maneuver, thus needing guidance from a sign and pavement marking, usually a yield line/sign combination. If the right turn lane is not separated from the adjacent travel lane by an island, the right turn movement is typically controlled by the signal head the driver is facing and a stop line, instead of a yield line/sign combination. Thanks for your comment!

      Reply

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