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24 CHAPTER 3 Methodology This chapter describes the field data collection methodol- when to begin crossing. Participants were accompanied at all ogy used in this research. It discusses the experimental design times by a certified O&M specialist. If a participant decided to and field methodology that were used to collect data with blind begin crossing at a time that the specialist judged to be unsafe study volunteers at the test locations. It further discusses the based on vehicle positions and speeds, the O&M specialist process of identifying and selecting treatments, which ulti- stopped the participant, usually by grasping the participant's mately led to the decision of which treatments should be tested arm or shoulder. This is referred to as an O&M intervention and in the field. The chapter then presents a summary of the site is later used as a safety performance measure in the analysis. selection process and describes the treatment and sites used in The same O&M specialist was used in all experimental trials the NCHRP Project 3-78A studies. performed in this research to ensure uniformity of instruc- tions and consistency in behavior, particularly as related to O&M interventions. Experimental Design After all participants had completed the pretest, treatments and Field Methodology were installed. The posttest was conducted after a driver adap- The general procedure used for crossing trials replicated tation or acclimation period, which allowed drivers to become field methodologies from previous work by research team familiar with the treatments. The posttest procedure was iden- members. To determine the effect of treatments, a pretest tical to the pretest procedure, except for changes related to posttest, within-participant design was used. In other words, the treatments (for example, pushing the push button on the participants were recruited to complete pretest crossings, and pedestrian hybrid beacon). then returned for a second study (posttest) after one or more treatments were installed at the site. This experimental design Participants allowed the team to control for confounding factors. By using the same participants for baseline and after-treatment data Participants were individuals who were blind with light- collection, each participant served as his or her own control, perception or less vision and who had no ability to visually which provided more statistical power when using a relatively detect crosswalk lines, poles, objects, or vehicles. Participants small number of participants. Therefore, all participants in the were individuals who traveled independently using a long cane posttest had also participated in the pretest to allow for a direct or guide dog and reported that they typically crossed streets within-participant comparison, although not all participants independently. This was done in an attempt to draw a sample returned for the second round of testing. The same basic pro- of participants from an appropriate target population of blind cedure was used in all studies for this project. pedestrians who might cross at the experimental locations In each session, the participant made crossings back and outside of the studies. A local O&M specialist in each city forth on each experimental crosswalk, using a white cane and assisted in recruitment of participants based on these criteria. determining when to begin crossing independently. Partic- Participants who were guide dog users were also proficient ipants were assisted with aligning to cross or maintaining in long cane use. All participants used a long cane during the alignment during crossings, as needed. Only one individual crossings because repetitious street crossings are confusing participated at a time, completing a number of crossings in for guide dogs. Participants were identified by recruitment each session. As in previous studies, participants were allowed coordinators and screened via a phone interview to determine to cross at their own pace and using their own judgment of if they met the criteria for the research. Written consent was