Impacts of Led Brightness, Flash Pattern, and Location for Illuminated Pedestrian Traffic Control Device

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INTRODUCTION

Illuminated traffic control devices, such as rectangular rapid-flashing beacons (RRFB), have been shown to increase the number of drivers yielding to crossing pedestrians. Evaluations of field installations of these devices have been conducted in several locations, including Florida, Texas, Oregon, Michigan, Arizona, Wisconsin, and Calgary, AB. (See references 1 through 10.) Before-after studies have shown a large increase in driver yielding between the before period (range of 1 to 83 percent) and the after period (range of 38 to 98 percent). While driver yielding has always increased after the RRFB installation, there are still examples of low yielding in some locations. Studies have shown a wide range in driver yielding to the RRFB, with values extending from a low of 22 percent to a high of 98 percent.

There is growing interest in adding the RRFB to the Manual on Uniform Traffic Control Devices (MUTCD).⁽¹¹⁾ The Signals Technical Committee of the National Committee on Uniform Traffic Control Devices, which assists in developing language for chapter 4 of the MUTCD, is interested in research to support proposed language for inclusion of RRFBs in the manual. To achieve the uniformity desired in the MUTCD and provide guidance that results in the best driver yielding behavior, several details require research. These details include beacon size, shape, color, placement location, brightness, and flash pattern. There is some concern that the brightness of flashes at or contained within signs at night may make it difficult for drivers to detect and observe the movements of pedestrians at the crossing. To prevent devices from being set at brightness levels that produce disability or discomfort glare, the profession needs to quantify the effect of illuminated traffic control devices on a driver’s ability to detect pedestrians in and around the crosswalk.

This TechBrief describes the methodology and results from a closed-course study sponsored by the Federal Highway Administration (FHWA) that addressed brightness, flash patterns, and location of light-emitting diodes (LED). It examined driver detection of cutout pedestrian photographs in the presence of LEDs of various brightness levels and flash patterns, which are placed in different locations within the sign assembly.⁽¹²⁾