PIETON

In a context of general aging of the population and the implementation of policies in favor of active transport, the mobility of the senior pedestrian is attracting attention both as a component of aging well but also as a risk factor for falls or accidents.

The overall aim of this thesis is to improve knowledge of potential risks, on the one hand, those related to street-side positioning prior to a crossing and, on the other, the motor consequences of confronting a hazard on the proximal path when initiating walking.

The first study was carried out in a street-side setting. Compared with young adults, some older pedestrians open the left foot outwards more, facilitating exploration of the proximal pathway. Laboratory studies of body sensations show that this positioning with the left foot open solicits less neck rotation but slightly more hip rotation; it also gives a better sensation of stability. In situ, it was also found that some elderly pedestrians position themselves further back from the kerb. Attempting to pinpoint the causes, a laboratory study reveals that seniors whose walking shows signs of motor decline underestimate the length of their first step, possibly due to insufficient updating of the internal action model.

Modeling the delayed discovery of an approaching vehicle during crossing initiation, two further laboratory studies investigated the impact of lateral onset of emotional stimulation conditioned by heel lift. In the first study, medio-lateral displacements compatible with withdrawal behavior were described for the first two steps, irrespective of age. Repeated in young adults with a later presentation of stimuli (as a consequence of faster walking), the data show an approach behavior during the second step. This result is linked to attentional capture by emotional images rather than a reactive effect probably closer to in situ reactions.

While the literature on decision training in older pedestrians is inconclusive, awareness of the critical behaviors we observe at the roadside could be easier and therefore more effective. As it stands, the interest of the data concerning the impact of emotions on the initiation of walking is more in the realm of fundamental research. The capitalized results suggest extensions whatever the study, but also avenues for methodological enhancement.