## 4 Discussion (Study 1)  
Clinicians need tools to evaluate and assess the performance skills used to complete the multifaceted task of driving including focal vision, peripheral vision, visual scanning, visual discrimination, following directions, processing speed, divided attention, selective attention, mental flexibility, eye/hand/foot coordination, motor planning, and endurance, to name a few. The FOD--Advanced (FOD-A) task is a tool designed to allow clinicians to meet their clients' complex and variable needs. The purpose of study 1 was to determine if the four FOD-A combinations differ in terms of difficulty and how the combinations can be rank ordered regarding their difficulty from easiest to hardest in order to provide clinicians with guidance for grading the task. Our findings suggest that three outcome variables should be considered first due to the ability to maximally distinguish performance among participants. Average target E reaction time was observed to be the most important variable, followed by percent of target Es detected, then average brake reaction time. This means that prior to considering any other variable, clinicians should first evaluate the client's average target E reaction time, then the percent of Es accurately detected, then the average brake reaction time. The ability to discriminate between driving simulator tasks is pertinent as clinicians must evaluate clients under restrictive conditions, such as time-constraints and limited screening instruments [55]. As such, this study provides support for clinicians to prioritize these variables to ensure their assessments are both quick and effective. Moreover, the results of the LDA revealed that performance differences existed between the FOD-A combinations 1 and 2, and combinations 1 and 2 differed from combinations 3 and 4. Consequently, the FOD-A combinations can be rank ordered from easy to hard as follows: combination 1, combination 2, followed by combinations 3 and 4. These results indicate several key contributions. First, we provide empirical evidence that the FOD-A combination utilizing cruise control with no distractor tasks (combination 1) is easier than manual control with no distractor tasks (combination 2). This not only presents an initial assignment that clinicians can use as a foundation to evaluate driving execution, but by increasing the difficulty via distractor tasks, this also supplies a metric to measure differences within the clients' performance. Second, the results also suggest that distractor Es (i.e., the task added to options 3 and 4) could be the reason for a significant difference in difficulty. This demonstrates the efficacy of using distractor symbols (e.g., E) as metrics of increased difficulty in driving simulations. Conversely, combinations with no distractor tasks are easier than combinations with distractor tasks, providing the basis for clinicians to reduce difficulty levels when needed. Additionally, combinations with the target Es that pop onto the screen (combination 1 and combination 2) are easier than combinations where the target E fades onto the screen (combinations 3 and 4), suggesting the need for visual acuity to be measured in conjunction with these tasks. A one-way MANOVA revealed that the FOD-A combination does have a univariate effect on driving simulator performance for these five variables: average target E reaction time, average brake reaction time, average speed, percent of target Es detected, and the number of target E extra presses. Subsequent analyses revealed that average target E reaction time significantly increased with each combination from 0.8 in combination 1, to 0.9 in combination 2, to 1.7 in combination 3, and to 1.9 in combination 4. This suggests that the increasing difficulty of the tasks led to an incremental rise in workload, and consequently, higher reaction times. The average brake reaction time for combination 1 was significantly lower compared to combinations 2, 3, and 4, reaffirming that less tasks to complete could be attributed to less workload.