Many senior drivers begin to experience physical limitations long before they lose their driving skills. Decreased strength, balance, and flexibility, for example, lead to some subjects experiencing an increased challenge, such as getting in and out of vehicles [1,2]. As people age, there are obvious physical changes, namely, at the psychomotor level and the biomechanical level of the musculoskeletal system, which are the origin of decreases in strength, motor coordination, balance, and precision of body movements [3,4,5,6].The National Center for Injury Prevention and Control (part of the Centers for Disease Control and Prevention) in Atlanta estimates that.
Annually, in the United States of America (USA) alone, about 37,000 seniors suffer injuries when entering or leaving vehicles; 40% of these injuries are due to falls. People aged 65 and over are ten times more likely to be hospitalized for injuries sustained while getting in and out of cars than younger people. Women are significantly more likely to be hospitalized. The probability of the injury occurring while exiting the vehicle is more than twice that of entering .Considering that the senior population is increasing worldwide  and that there is a high number of older drivers qualified to drive , improving the experience of getting in and out of a car is a challenge for designers, planners, and engineers who are exploring solutions that improve automotive design, adjusting it to the limitations arising from the natural aging process of users [10,11].Entering and exiting a car are complex, multisensory experiences involving coordination, balance, and body movement. These bodily movements are usually performed without premeditation, and the body, through the psychosomatic experience, ends up adapting to the envelope and shape of the car .
The bodily movements associated with the process of getting in and out of a car–bending, twisting, stretching, and tipping–create high biomechanical stresses [13,14]. Several aspects of psychomotor functioning decline with increasing age. Deficits in psychomotor functioning increase the difficulty in controlling movement when sitting down and standing up, as well as the difficulty in maintaining balance whenever the positioning of the trunk weight is varied. Some cognitive slowdowns, joint stiffness, and muscle weakness decrease reaction time and induce slower biomechanical movements . Leg stiffness originates from states of imbalance in terms of body positioning .Previous investigations [16,17] reveal that the experience of entering and leaving represents the initial interactions that the customer has with the vehicle and, therefore, constitutes a fundamental influence on the purchase decision. Car usability for the entry and exit process also requires particular attention, as the number of drivers who report discomfort in cars is still significant. Other authors [8,18] also add that minimizing the requirements and stress patterns arising from usability in the vehicle entry and exit process improves customer satisfaction.In the past, car manufacturers conducted surveys to assess customer satisfaction regarding the entry and exit process of their car models. These questionnaires had the clear objective of assessing opinions about the ease of the entry/exit movements for their target audience, with a view to improving the development of future vehicles [19,20].
The answers obtained indicated a need to develop prototypes or physical models on a real scale with the purpose of testing the entry and exit movements required for the car. Using these evaluation methods (with questionnaire and prototype construction), the results suggested, for the most part, limitations correlated with the dimensions of the vehicles . However, the high costs associated with the construction of non-reusable prototypes, the high number of individuals needed to carry out the studies (for the sample to be representative), and the subsequent data analysis have, to date, made this practice costly and not applicable . Currently, car manufacturers focus on delimiting any problems related to a car’s entry/exit process, even during the design phase . The evaluation of accessibility movements required to enter and exit a car is carried out, essentially, through simultaneous engineering, with evaluation methods that use numerical mannequins, which help to reduce costs and production delays  significantly. Numerical dummies provide virtual models of the human user, capable of representing and even predicting their behavior (user interaction with physical interfaces and the environment). The use of these models makes it possible to analyze and evaluate automotive ergonomics and, in this way, deduce the requirements of the user . However, the movement strategies adopted in the simulator are restricted and do not allow covering of the universe of possible users .To better understand human behavior, it is important to carry out detailed ergonomic analyses and anthropological studies and, only afterward, simulate human movement. Research on the movement strategies adopted by users is an essential first step towards an accurate simulation [23,26]. The procedures used to determine movement strategies can be divided into two categories: (i) qualitative procedures based on observation and (ii) quantitative procedures based on automatic calculations .
Constant technological improvements increase the potential of virtual reality techniques in computer simulation programs used by the automotive industry [24,27,28]. Interactive simulated environments can be created using virtual reality techniques, which allows a quick assessment of the usability of the various project alternatives. This technology is particularly promising in anticipating and solving problems that are being considered in the design phase. The great difficulty is the correct integration of the virtual simulation in the design phase . Several researchers [25,27,28,30] suggest, as the most recommended methodology, the use of motion capture from optoelectronic systems with passive markers to measure the bodily movements of automobile accessibility. Although optoelectronic systems may have some instrumental and experimental errors, they are still among the most suitable systems for the study of complex motions.The analysis of accessibility movements associated with a car also includes quantification and classification of the movements by strategies, with the aim of refining the results of the analysis of the identified motor strategies to simulate the movement faithfully .
Some studies of car accessibility consider all entry and exit movements [32,33]. Others limit their scope to either entry [34,35,36] or exit . Some studies analyze movement strategies through the complete study of the human body, while others are focused on specific parts of the human body, namely, the head [2,21,37] and the trunk .
Other studies highlight the influence of some parts of the vehicle on car accessibility movements, such as the door sill , seat height , and roof height [21,38]. Recent studies have used a mock-up with the motion data acquired by the optical motion capture system. However, the differences observed in movement strategies only provide clues for future studies [32,39]. In this area of study related to the bodily process of getting in and out of the car, investigations based on observational methodologies have proven to be very useful in increasing the understanding of human behavior.
However, the observation procedures do not provide accurate results, as they have a shortcoming in the lack of numerical reference marks essential to quantify and measure what is observed. Thus, research methods based on observation require great experience and knowledge to implement measures that effectively mitigate the observed results [19,31]. Other visual methods of motion analysis classify by mapping them into two-dimensional planes according to the similarities between them [35,40].This research using visual analysis has the advantage of allowing the user to spontaneously observe entering/exiting a real car that has never been experienced before, although with the limitation of analysis in a single observation plane, without quantitative measurements. It will make it possible to analyze the movement strategies adopted by many subjects, who may not get in and out of the car most easily because of their height and physical condition and the vehicle’s geometry. Therefore, if they are experiencing difficulties, they are likely to try to change their technique and look for ways to support their torso or hands to increase balance and reduce discomfort.