Drivers with Alzheimer disease (AD) exhibit a range of performance on tests of cognition, vision, and motor skills. Since these tests provide additional predictive value of driving performance beyond diagnosis alone, clinicians may use these tests to help predict whether a patient with AD can safely operate a motor vehicle.

Overall, drivers with Parkinson disease (PD) had poorer road safety compared to controls, but there was considerable variability among the drivers with PD, and some performed normally. Familiarity with the driving environment was a mitigating factor against unsafe driving in PD. Impairments in visual perception and cognition were associated with road safety errors in drivers with PD.

Objective: To assess driving performance in Parkinson disease (PD) under low-contrast visibility conditions. Methods:Licensed, active drivers with mild to moderate PD (n ϭ 67, aged 66.2 Ϯ 9.0 years, median Hoehn-Yahr stage ϭ 2) and controls (n ϭ 51, aged 64.0 Ϯ 7.2 years) drove in a driving simulator under high-(clear sky) and low-contrast visibility (fog) conditions, leading up to an intersection where an incurring vehicle posed a crash risk in fog.Results: Drivers with PD had higher SD of lateral position (SDLP) and lane violation counts (LVC) than controls during fog (p Ͻ 0.001). Transition from high-to low-contrast visibility condition increased SDLP and LVC more in PD than in controls (p Ͻ 0.01). A larger proportion of drivers with PD crashed at the intersection in fog (76.1% vs 37.3%, p Ͻ 0.0001). The time to first reaction in response to incursion was longer in drivers with PD compared with controls (median 2.5 vs 2.0 seconds, p Ͻ 0.0001). Within the PD group, the strongest predictors of poor driving outcomes under low-contrast visibility conditions were worse scores on measures of visual processing speed and attention, motion perception, contrast sensitivity, visuospatial construction, motor speed, and activities of daily living score. Conclusions:During driving simulation under low-contrast visibility conditions, drivers with Parkinson disease (PD) had poorer vehicle control and were at higher risk for crashes, which were primarily predicted by decreased visual perception and cognition; motor dysfunction also contributed. Our results suggest that drivers with PD may be at risk for unsafe driving in low-contrast visibility conditions such as during fog or twilight. Neurology Reduced contrast sensitivity (CS) is a common feature of Parkinson disease (PD)1-11 and is associated with poor outcomes on driving tests in parkinsonian drivers.12-14 However, there are no published reports on driving under low visibility due to low-contrast lighting conditions in PD. This study evaluates the effect of different environmental visibility settings (high contrast ϭ clear sky, low contrast ϭ fog, as in figure 1) on vehicle control (indexed by SD of lateral position [SDLP] and lane violation counts [LVC]) during uneventful driving, and response to sudden hazards under low-contrast visibility conditions in drivers with PD using a driving simulator.To test driver response to a sudden hazard under low-contrast visibility conditions, we used a collision avoidance scenario at an intersection. [15][16][17] Although intersections constitute only a

Ecstasy (MDMA) use raises concerns because of its association with risky driving. We evaluated driving performance and risk taking in abstinent recreational MDMA users in a simulated car following task that required continuous attention and vigilance. Drivers were asked to follow two car lengths behind a lead vehicle (LV). Three sinusoids generated unpredictable LV velocity changes. Drivers could mitigate risk by following further behind the erratic LV. From vehicle trajectory data we performed a Fourier analysis to derive measures of coherence, gain, and delay. These measures and headway distance were compared between the different groups. All MDMA drivers met coherence criteria indicating cooperation in the car following task. They matched periodic changes in LV velocity similar to controls (abstinent THC users, abstinent alcohol users, and non-drug users), militating against worse vigilance. While all participants traveled approximately 55mph (89kph), the MDMA drivers followed 64m closer to the LV and demonstrated 1.04s shorter delays to LV velocity changes than other driver groups. The simulated car following task safely discriminated between driving behavior in abstinent MDMA users and controls. Abstinent MDMA users do not perform worse than controls, but may assume extra risk. The control theory framework used in this study revealed behaviors that might not otherwise be evident.

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