First things first, before having someone drive a prototype, it is important to know about his/her condition. Of course, the doctor is the main source of information, but in order to process results afterwards, some index is always useful, we are engineers, after all!!. The key is to obtain a quantified disability profile to correlate this data with the amount of help they may require, demand or receive.

Disability is technically defined as a lack of ability relative to a personal or group standard or norm, but, in fact, there is often simply a spectrum of ability. It may involve physical, sensory, cognitive or intellectual impairment, mental disorder and/or various types of chronic disease.

In experimental work, though, it is better to define disability as the degree of difficulty to independently perform basic Activities of Daily Living (ADL) [Katz]. Disability is not an attribute that is clearly present or absent, but rather a matter of degree.

One of the best ways to obtain global information about patient needs is represented by the multi-dimensional approach and, in particular, in case of elderly patients the most common approach is the CGA, a multidimensional process designed to assess an elderly person's functional ability, physical health, cognitive and mental health, and socio-environmental situation. It includes different disability scales to evaluate the cognitive and physical state and condition of individuals. Here are the most popular ones.

The MMSE or Folstein test [Crum] is a brief 30-point questionnaire test that provides a quantitative measure of cognitive status in adults. Any score
over 27 (out 30) is effectively normal, event though it changes depending on age and education. In the time span of about 10 minutes, it samples various functions, including arithmetic, memory and orientation.

IADL, also called Lawton's scale [Lawton], is based on a questionnaire to evaluate the capacity of the subject to perform daily tasks ruled by cognitive functions (judgement, language, orientation, calculation, memory, planning). Thus, IADL measures the degree of autonomy of an elderly individual. This test appears complementary to MMSE, that rather evaluates cognitive functions. For example, a subject with memory disorders or difficulty of calculating shows a reduced score. 4 tests are particularly important since they are well correlated with cognitive functions evaluated by the MMSE test. They include the ability to : i) Use telephone; ii) Use transportation; iii) Take medication; and iv) Handle finances. For example, using a telephone under his own initiative is related to the intention and planning of a task (to look up the name of somebody in a phone book) and to the comprehension of language (to have a conversation). On the other hand, to be limited to a small number of well known phone numbers or to answer the telephone without calling implies automatic mechanisms. An evaluation of these 4 activities allows early detection of cognitive deterioration, several years (approximately 3 to 5) before a dementia is diagnosed. Detection of an alteration of at least one of these 4 activities calls for a more precise neurological assessment.

The GDS [Yesavage] is a self-report inventory, constructed to assess depression and general well-being in the elderly. It is a brief questionnaire in which
participants are asked to respond yes/no to 30 questions in reference to how they felt on the day of administration. Scores of 0-9 are considered normal, 10-19
indicate mild depression and 20 - 30 indicate severe depression.

The Barthel Index [Mahoney] consists of 10 items that measure a person's daily functioning, specifically ADL and mobility. Items can be divided into a
group that is related to self-care (feeding, grooming, bathing, dressing, bowel and bladder care, and toilet use) and a group related to mobility (ambulation, transfers, and stair climbing). The maximum score is 100 if 5-point increments are used,
indicating that the patient is fully independent in physical functioning. The lowest score is 0, representing a totally dependent bedridden state.
Apraxia is a neurological disorder characterized by loss of the ability to execute or carry out learned purposeful movements, despite having the desire to and the physical ability to perform the movements. It scores from 0 (worse result) to 10.