Pedestrian Signals: Visibility to Pedestrians with Varying Levels of Vision
RESEARCH PROBLEM STATEMENT
In an increasingly complex pedestrian environment, where the pedestrian phases may not be concurrent with vehicular green, recognition of pedestrian signal indications is necessary. Safe initiation of pedestrian crossing at signalized intersections depends on both knowledge of the onset of the walk interval, as indicated by the pedestrian signal indication, and on the ability to simultaneously monitor conflicting movement of vehicles that may be turning across the crosswalk or that may be running the red light.
Persons having reduced visual fields may particularly have difficulty locating pedestrian signals in a visually cluttered background. Persons having low acuity often have difficulty discriminating the signal information. While it is assumed that color provides a helpful cue to discriminate pedestrian signal information, low vision may affect ability to discriminate color under varied lighting conditions. Usability of pedestrian signals by pedestrians with low vision appears to be influenced strongly by differences in lighting and glare.
In order to judge a safe time to begin crossing, pedestrians need to simultaneously use signal information and be aware of vehicular threats that should inhibit crossing at the onset of the WALK signal. Older pedestrians typically have decreased contrast sensitivity and visual acuity, reduced peripheral vision, and reduced “useful field of view,” (Wilson and Grayson, Age-related differences in the road crossing behavior of adult pedestrians, Publication No. TRRL-L-933, Transport and Road Research Laboratory, Crowthorne, England, 1980), all of which may affect their ability to use pedestrian signal information while simultaneously monitoring vehicular movement. Twenty-five percent of older persons surveyed in Orlando, FL reported that they had difficulty seeing pedestrian signals (Bailey, Jones, Stout, Bailey, Kass, and Morgan, 1992, Issues of elderly pedestrians. Transportation Research Record 1375).
The MUTCD 2003 and the ITE Pedestrian Traffic Control Signal Indications – Part 2 provide minimal requirements and guidance on how to make pedestrian signal indications usable by pedestrians. Six inch high symbols are permitted for all crossings up to 100 feet in length, although MUTCD 4E.04 says “Pedestrian signal head indications should be conspicuous and recognizable to all pedestrians from the beginning of the controlled crosswalk....” Symbol colors and shapes are standardized in MUTCD 4E.04, and minimum brightness values for day and night viewing are provided in the ITE Standard.
LITERATURE SEARCH SUMMARY
No research has been identified on the ability of pedestrians to use information provided by pedestrian signals varying in size or brightness, in the context of crossing decisions.
Two recent projects have considered recognition distance of pedestrian signals of different shapes by pedestrians with low vision (Van Houten, Blasch and Malenfant. A comparison of the recognition distance of several types of pedestrian signals with low vision pedestrians, 2001, Journal of Rehabilitation and Development Research 38(4); Williams, Van Houten and Blasch. Field comparison of two pedestrian signals on recognition distance of low vision pedestrians. Presented at Transportation Research Board, January 2005). In both of these studies research was conducted in daytime only, in the context of a relatively uncluttered background, and with signals always in the same location, so there was minimal visual challenge for locating the signals. Results of these studies were contradictory.
Research by Finley (Visibility performance requirements for pedestrian signals. Presented at Transportation Research Board, January 2005) manipulating brightness of LED pedestrian signals validates the ITE recommendations and indicates that a good starting point for the proposed research is the ITE minimum recommended values under day and night conditions.
Three studies have examined perception-reaction time of pedestrians at signalized intersections, however the nature of the signal indications, ambient light, and background complexity were not systematically varied, and pedestrians with reduced vision were not intentionally included in the samples (Knoblauch, Nitzburg, Dewar, Templer and Petrucha. Older pedestrian characteristics for use in highway design. Publication No. FHWA-RD-93-177, Federal Highway Administration, 1995; Fugger, Randles, Stein and Gallegher. Analysis of pedestrian gait and perception-reaction time at signal-controlled crosswalk intersections. Transportation Research Record 1705, pp. 20-25, 2000; Parsonson. Signal timing improvement practices, NCHRP Synthesis of Highway Practice 172, 1992).
To determine the usability of pedestrian signals in the context of decisions regarding starting to cross, by persons with varying amounts of vision, and types of low vision, under different conditions of signal design, ambient light, and background clutter. Results will be used as the basis for proposing revised language for MUTCD 4E.04 and 5, and ITE Pedestrian Traffic Control Signal Indications – Part 2, and to prepare a guidance document regarding design and installation of pedestrian signal indications to make them maximally useful to all pedestrians who make street-crossing decisions based primarily on visual information.
1. Literature and field search resulting in a synthesis on usability of pedestrian signal information in the context of decision making for street crossing.
2. Human factors testing using large format video technology to examine the effects of signal size, illumination and background clutter, including movement of conflicting vehicles, on crossing decisions by pedestrians with varying levels of vision.
3. Field testing of recommendations resulting from the laboratory research.
3. Preparation of guidelines for pedestrian signals and installation, including case studies.
4. Development of language for inclusion in the MUTCD and ITE Pedestrian Traffic Control Signal Indications – Part 2.
ESTIMATE OF PROBLEM FUNDING AND RESEARCH PERIOD
Recommended Funding: $600,000.
Research Period: 3 years
URGENCY, PAYOFF POTENTIAL, AND IMPLEMENTATION
The growing elderly population in the U.S is likely to result in larger numbers of individuals who are unable to drive because of impaired vision, many of whom can be expected to use public transit or walking as a primary means of travel. It is estimated that by 2010 there will be 20 million visually impaired persons in the U.S. over the age of 45. Results of this research will increase the guidance available to practitioners installing pedestrian signals and lead to language in the MUTCD that will provide improved safety in crossing decisions by pedestrians having varying amounts of vision.
Members of the research team will present results of research to the NCUTCD and at ITE, They will propose language, to be approved by the Panel, and will assist in following through changes to be made in the MUTCD and in ITE Pedestrian Traffic Control Signal Indications – Part 2.