Intersection Worksheet Variables

Configuration

Pedestrians who are blind or visually impaired use the sound of traffic moving beside them as an alignment cue and as a cue for determining when the traffic signal changes. Therefore, the number of approaches to an intersection and the geometric configuration affects the difficulty of crossing. A standard 4-leg intersection with perpendicular approaches is the easiest configuration. If those approaches are offset while still controlled by the same signal, the crossing becomes more difficult as it becomes harder to recognize the parallel traffic flow from the minor street. T-intersections are more difficult for similar reasons. Crossing the top of a T-intersection can be problematic due to the fact that the simultaneous traffic flow is from the stem of the T and is either turning right or left. Intersections with more than 4 legs can also result in ambiguous traffic flow cues for pedestrians with visual impairments.

Mid-block signalized locations are most difficult for blind pedestrians because there is no traffic stream parallel to the crosswalk to provide an audible cue. Given this, signalized mid-block crosswalks receive the highest point value in the Configuration category (14 points). Since completing the remainder of the worksheets for a mid-block crossing may prove confusing, the categories that apply to a mid-block crossing have been listed in Table 1 below.

[Display Variables Table]

Intersection Worksheet Variable

Applies to Mid-Block Crossing?

Configuration

Yes

Signalization

Yes, Actuated

Transit Facilities

Yes

Distance to Facilities for Visually Impaired

Yes

Distance to Major Ped Attraction

Yes


Crosswalk Worksheet Variable

Applies to Mid-Block Crossing?

Crosswalk width

Yes

Posted Speed Limit

Yes

Curb radius > 25 feet

No

Islands or medians

Yes

Transverse slope

No

Apex curb ramp

No

Channelized right turn island

No

Skewed crosswalk

No

Pushbutton actuation required

Yes

Non-concurrent WALK interval

No

Leading Pedestrian Interval

No

Timed for crossing to median island

Yes

RTOR permitted

No

Leading protected left turn

No

Protected right turn overlap

No

Channelized right turn under signal

No

Off-Peak Traffic Presence

Yes

Pushbutton location

Yes

Requests for APS

Yes

[Hide Variables Table]

Signalization

The sequence of phases at a signalized intersection and other features of the signal operation, such as interval lengths and actuation-only phases, affects the ability of a blind pedestrian to determine when it is appropriate to cross. This information is captured in two places. The Signalization variable captures information about the general signal operation that may affect the difficulty of crossing any or all streets. The Crosswalk Signalization variable on the crosswalk worksheet captures details about the signal operation that impact a particular crosswalk.

The following signalization options are given on the form. The user should select the option that has the highest point value AND applies to the intersection of interest. For example, if an actuated intersection has an exclusive pedestrian phase, then the user should select only "exclusive pedestrian phase", since that option has a higher point value than actuation.

Pre-timed — Pre-timed signalized intersections are the easiest for a blind pedestrian to understand, since the phase sequence and intervals remain the same in every cycle.

Actuated — Actuated signals are more difficult for blind pedestrians since the interval timing may change or phases may be skipped on each cycle. In addition, some actuated signals require the pedestrian to find and push a pushbutton to obtain a WALK interval. Note: This intersection signalization variable is intended to capture actuation associated with vehicular traffic. Pedestrian actuation is captured within the Crosswalk Signalization variable on the Crosswalk Worksheet.

Split phasing (on either street) — The auditory cues of split phasing can provide confusing information. Split phasing on the street parallel to the crosswalk can lead a blind pedestrian to believe they have the WALK interval because the cross street traffic is stopped and they hear a surge on the parallel street, not knowing that left-turning vehicles may be present.

Figure D-1. Split Phase Illustration

Figure D-1. Split Phase Illustration

In the image on the left in Figure D-1, a pedestrian going north on the east crosswalk (bottom right corner) will have the WALK indication. A pedestrian going north on the west crosswalk (bottom left corner) will have DON'T WALK, since the northbound left turning traffic has a protected turn. Without APS, if a blind pedestrian on the bottom left corner hears the northbound through traffic, they might assume that they have the WALK indication and cross the street — presenting a potentially dangerous conflict with northbound left-turning traffic which has a protected turn.

Split phasing on the street to be crossed can also be confusing in that the left-turning traffic onto the parallel street may be mistaken for the parallel street traffic surge. This variable does not include leading protected left turns; that signal feature is covered as a crosswalk-level variable.

Exclusive pedestrian phase — An exclusive pedestrian phase forces all vehicular traffic at an intersection to stop. It is much more difficult for a blind pedestrian to determine the onset of a WALK interval when there is no vehicular movement and thus no surge of traffic. A lull in traffic flow may be perceived as the onset of the WALK. However, a lull in traffic may also be perceived as gaps in traffic or changes between phases, rather than the onset of an exclusive pedestrian phase.

Where RTOR is permitted in combination with exclusive pedestrian phasing, an intersection may never be quiet enough for pedestrians who are blind to be sure that the pedestrian interval has begun. If they cross at such intersections independently, they are likely to begin crossing well into the pedestrian clearance interval. Additional points should be added for RTOR (separate variable described below) when present.

Transit Facilities within a Block (~ 1/8 mile) of Intersection — Any Leg

The availability of transit facilities within close proximity to an intersection will increase the likelihood of blind pedestrians, as well as sighted pedestrians, crossing at that intersection. The probability increases as the number of stops and routes increases, with the greatest probability occurring when there is a major transfer facility present, such as a transit mall or rail station. The levels on the prioritization tool account for transit activity by recording the number of routes that have stops within a block of the intersection. A single route will most likely be on the major street of an intersection. Multiple routes may include multiple major-street routes or a combination of major- and minor-street routes.

Distance to Facility Providing Services to the Blind or Visually Impaired

The closer a facility for persons who are visually impaired is to an intersection, the more likely it is that pedestrians who are blind or visually impaired will need to cross at that intersection. Facilities that fall into this category include an adult rehabilitation center, library for the blind, residential school for the blind, offices of rehabilitation counselors, and other centers providing services for people who are blind or visually impaired.

Knowing the locations of these facilities will be difficult for any transportation department without good communication with the blind community. It is the responsibility of the department and the blind community to maintain a working relationship with each other. Organizations such as regional associations for the blind would be able to inform the department of any new schools or facilities that provide services to persons who are blind or visually impaired.

Distance to Major Pedestrian Attractions

The intent of this variable is to serve as a surrogate measure for pedestrian usage at the intersection without having to make pedestrian counts. Most agencies simply do not have such counts or the resources to acquire such. Major pedestrian attractions include, but are not limited to major shopping areas, major cultural venues, educational campuses, recreational areas and medical facilities. The designation of "major attraction" will depend on the characteristics of the municipality. The idea behind this variable is that higher pedestrian activity will increase the chance of blind or visually impaired pedestrians crossing at the intersection, which would increase the need for APS.

[ back to top ]