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Field Adjustments

Changes in the travel environment

Types of changes
In the past twenty years, significant changes in intersection geometry, signalization, driver behavior, and the technology of automobiles have affected the ability of blind travelers in the United States to use the above-mentioned techniques.

Intersection design changes
  • Wider streets require more precise alignment.
  • Wide radius turns make alignment more difficult and increase crosswalk length.
  • Curb ramps and depressed corners make street detection and alignment difficult.
  • Medians and islands complicate wayfinding and alignment.
  • Slip lanes and splitter islands require crossing in gaps in traffic even at signalized intersections.
  • Crosswalk alignment is not consistent.
  • Curb extensions, also called bulb-outs or intersection chokers, sometimes complicate wayfinding.
  • Raised crosswalks may obliterate the sidewalk/street boundary.
  • Tabled intersections may also obliterate the sidewalk/street boundary.
Driver behavior and technology of autos
  • Aggressive drivers are moving faster and less likely to stop for pedestrians.
  • The technology of cars, including electric cars, has become quieter, making them harder for pedestrians who are visually impaired to hear.
  • In many areas there is less pedestrian traffic and less awareness of pedestrians by drivers.
Signalization changes
Intersection signalization has become more complex.

The techniques which worked at pretimed lights controlled by mechanical controllers are not adequate for intersections which change minute by minute in response to vehicular and pedestrian actuation. These changes affect the ability of pedestrians who are blind or visually impaired to recognize the pedestrian phase.


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