This study built upon the findings of recent problem identification research conducted for NHTSA that documented the prevalence of pedal application errors–specifically, the driver error of mistaking the accelerator pedal for the brake pedal–and the driver, vehicle, roadway, and environmental characteristics associated with these crashes. The prior study included a literature review; an analysis of 3,341 pedal misapplication crashes with 899 from media reports, 2,411 from the North Carolina Department of Motor Vehicles, and 31 from the National Motor Vehicle Crash Causation Survey; and a meeting with certified driver rehabilitation specialists (CDRSs). The analysis of news media reports over the past 10 years provided an estimate of 15 pedal misapplication crashes per month in the United States, and analyses of the NCDMV and NMVCCS crash databases suggested these driver errors were a factor in less than 1% of all crashes. However, the researchers identified limits to the reporting and archiving of these events that could result in underestimation. The literature review found only sparse evidence of the frequency of pedal application errors. Two predictors for pedal error events were identified: greater driver age and impairment in driver’s “executive function.”1 These studies also demonstrated that pedal misapplications could be triggered by sudden changes in the environment that startled drivers. However, the studies included in this review were all conducted with driving simulators therefore may not reflect real-world driving behavior. One simulator study found that older drivers’ right foot movements were more variable than those of younger drivers when moving from the accelerator to the brake. Older drivers had significantly greater foot movement amplitudes, and they made several sub-movements of the right foot following the release of the accelerator. Younger drivers rarely made such sub-movements. The authors noted that more research was needed to determine if there is a direct relationship between variability in lower limb movement and pedal misapplications. Lococo, Staplin, Martell, and Sifrit (2012) found that crash involvement plotted against driver age produced a U-shaped function showing significant over-involvement by the youngest (age 16 to 20) and oldest (76+) drivers. In the media analysis as well as in the NCDMV crash database analyses, older drivers were more likely than other drivers to be performing a parking maneuver prior to making a pedal application error. In all three analyses, females accounted for nearly two-thirds of crashes resulting from pedal misapplication. Driver inattention and distraction were common contributing factors across all age groups. Pedal misapplication crashes described in the news media reports and in police narratives from the crash databases often mentioned situations that startled drivers or included a panic braking response. A panel of driver rehabilitation specialists (DRSs) convened during the earlier NHTSA study provided another perspective. Panelists drew on their clinical experience to discuss the medical conditions and functional deficits, the maneuvers, the locations, and the driving task demands associated with pedal application errors. The panel indicated most pedal application errors they observed in their clients occurred in parking lots. DRSs noted that their clients manifested one or more impairments that could undermine their driving abilities, so it is to be expected that they would have the greatest difficulty–and experience the greatest number of incidents–in parking lots where there is less room to recover/correct a pedal misapplication given the proximity of cars and other objects. The DRSs hypothesized that many more pedal misapplications may occur on-road than showed up in the media and crash analyses because drivers had the time and space to correct the error and avoid crashing. The DRS panel identified three general populations of drivers they considered likely to make pedal application errors: (1) those with sensory defects in their feet; (2) those with cognitive limitations; and (3) those with no specific medical conditions or functional impairments but whose driving performance was undermined by other factors (e.g., inexperience, misfit in the vehicle, unfamiliar vehicle, distraction). DRSs expressed particular concern about peripheral neuropathy as a potential cause of pedal application errors. Panelists indicated that over the past 10 years increasing percentages of their referred clients reported difficulty feeling their pedals. Approximately 8 to 9% of Medicare recipients carry neuropathy as either a primary or secondary diagnosis–about 20 million people–yet neuropathy is one of the least recognized conditions in the United States. The panelists noted that many of their clients were unaware that they had a loss of sensation in their feet. Although hip and knee replacements, as well as many medical conditions and some medications can cause peripheral neuropathy, it may nevertheless be the case that physicians and occupational therapists do not test patients for sensation in their feet. Panelists recommended physician education about medical conditions that can cause peripheral neuropathy, testing of patients for loss of foot sensation, and discussions between physicians and patients about the implications of peripheral neuropathy for driving. They recommended that physicians refer patients with loss of sensation in their feet to driver rehabilitation specialists for evaluation. DRSs observed pedal application errors among their clients who performed poorly in clinical tests of executive function. They were familiar with the concept of sub-movements described in the earlier literature review. Many indicated that they had observed such foot “wandering” in cognitively impaired, older clients. DRSs commented that clients who began driving with both feet late in their driving careers were more likely to make pedal application errors, compared to those who had been driving with both feet their entire driving career. They noted an evolution from one- to two-footed driving among the cognitively impaired older driver population during their on-road evaluations, particularly in parking lots. In addressing the overrepresentation of women in pedal misapplication crashes, the panelists commented that women tend to be smaller and their “fit” in the driver’s seat is often poor. Many sit with their hips stretched forward, which can cause leg cramps as well as temporary loss of sensation in their foot and leg. These observations point to issues with the vehicle as a cause of pedal misapplications as opposed to a medical condition. At CarFit2 events, DRSs have often observed women sitting too far away from the steering wheel, sitting too low, reaching for controls, and stretching with their toes to reach the pedals. Pedal application errors can result in crashes. This issue is of particular concern for the aging population, whose members have been shown to be over-represented in pedal error crashes (Lococo, Staplin, Martell, & Sifrit, 2012), because they remain overwhelmingly dependent on the private automobile for the activities of daily living. This study refines the understanding of the relative contributions of cognitive and functional impairments on driver foot movements and describes when sensory loss significantly increases sub-optimal foot movements. This information will assist clinicians who perform driving evaluations and also help physicians and nurses determine when a referral to a CDRS for a driving evaluation is appropriate. This study was conducted to explore how older drivers use their feet to accelerate and brake during on-road driving and when parking a vehicle. Researchers obtained in-clinic measures of functional ability, and used an instrumented vehicle on a planned test route under normal traffic conditions to obtain measures of foot positioning behaviors for groups of drivers with and without selected medical conditions. The goal was to identify driver characteristics, including the degree of functional loss associated with medical conditions that could pose an increase in the risk of unintended accelerations or late/abrupt braking. Researchers documented participants’ height, upper and lower leg length (femur and tibia), and foot and shoe size to determine whether these factors were related to the way drivers used their pedals. For example, foot and/or shoe size could affect whether drivers pivot their foot or lift the entire foot when moving between pedals, which could affect speed and accuracy of foot movement and placement. An additional objective was to gain a greater understanding of how older drivers fit in their vehicles, and whether poor vehicle fit was associated with short stature and/or driver sex as mediating factors in driver foot movements, as suggested in the earlier study. Researchers documented each driver’s selected seat position in his or her own vehicle using a subset of the CarFit protocol as each arrived to participate in the study, as well as measures of the distance from the brake pedal to the driver’s hip point at the selected seating position. Safety considerations precluded researchers from collecting foot movements in the instrumented vehicle using self-selected seating positions matching the own-vehicle positioning if it was not optimal for safety. Therefore, the study did not address whether poor vehicle seating position was related to problematic foot positioning behaviors in the on-road driving portion of the study. Analyses addressed the following research questions: • Did foot position and/or variability in foot movement differ by medical status? • Did foot position and/or variability in foot movement differ by sex? • Was position and/or variability in foot movement related to driver height and/or shoe size? • Was poor driver-vehicle fit related to driver height or sex? • Was late/abrupt braking associated with a measured degree of functional loss associated with peripheral neuropathy? (Author/publisher)
Abstract