May 15


Aps 2 I spoke at this Wednesday's NCITE luncheon about Miovision's automated turning movement count system.  The luncheon had a technology theme.  In addition to my presentation, Sue Zarling with Mn/DOT spoke about accessible pedestrian systems and Jerry Kotzenmacher with Mn/DOT spoke about traffic signal enforcement lights.  Both talks were interesting.  I'll post about Sue's presentation here and Jerry's presentation next week.

Accessible Pedestrian Systems (APS) are meant to aid the sight impaired in crossing intersections that have traffic signals at them.  The pushbuttons have arrows and braille descriptions.  They also make a slight beeping sound to help the impaired locate them.  The system has a sound detector so the beeping fluctuates based on the ambient noise levels.  The beeping stays 5 decibels louder than the ambient noise level.  When the walk indication turns on for those with normal eyesight, the APS gives verbal instructions for the crossings.  It can also give a loud warning if an emergency vehicle is detected by the signal system. 

Mn/DOT has developed a specification for APS.  They have a document online to assist agencies in prioritizing which intersections to retrofit first with APS and they have developed a spreadsheet to assist in the programming of the system.  Also, a very thorough resource for APS is located on

A few concerns Sue brought up regarding APS:

  • It costs money.  The components alone cost about $5,700 per intersection, not including labor.
  • They can be noisy.  They add 5 decibels worth of noise within six to twelve feet of the pushbutton.
  • They require additional stub, pushbutton station poles which are prone to being hit by snowplows.
  • Each pushbutton is uniquely programmed for its location.  If one breaks, it takes a couple of weeks to get a replacement from the manufacturer.  This is a big maintenance issue.
  • You need someone who can read braille to make sure the pushbutton braille is correct.

There are conflicting judgments and legislation floating around.  In Mn/DOT's opinion, there isn't clear guidance for when APS  must be installed.  The State of Maryland and the City of San Francisco have both agreed to install APS through court settlements.  There are many open cases throughout the country, including in Minnesota, pushing for the installation of APS.  The United States Access Board has published draft guidelines that state APS systems shall be installed whenever new pushbuttons are being installed with a traffic signal. 

Mn/DOT's legal interpretation of all of this information is that each government agency needs to develop a policy for when they will and will not install APS.  They are currently drafting a Technical Memorandum to clarify their agency's position and design guidelines.  In a nutshell, Sue said they will be installing APS with all new signal systems and they are developing a ranking system based on the NCHRP guidelines for retrofitting their existing signals with APS.

  • I know of a few intersections in Portland that have the audio feature. The street that is crossed is a five-lane cross section that separates downtown from a riverfront park. I will look closer the next time I am in the area to see if they have braille in addition.
    What makes each push button unique? Does the braille have different script that details number of lanes and so forth?

  • Each push button has the street names in braille. Combining the street name with the directional arrow on the push button makes each one unique. Mn/DOT doesn’t do this, but you can go so far as to have a detailed map of the intersection imprinted on each push button.

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    Mike Spack

    My mission is to help traffic engineers, transportation planners, and other transportation professionals improve our world.

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