With the objective to understand passengers’ variation in lateral torso position relative seat centreline in real-world traffic situations, this study contributes with front seat passenger lateral sitting posture and comfort perception in two driving studies. In the first study, 26 participants travelled 40 minutes in a suburban area including turns with lateral accelerations of 1.3m/s²-3m/s². In the second study, 14 participants were exposed to low-force seat belt tensioning. The participants’ lateral torso, head positions and shoulder-belt positions, prior to and during the turn, in addition to perceived comfort and safety, were collected.

Prior to the turn, the majority had an inboard displaced position. In the turns with highest accelerations, the maximum torso lateral position during the turn was significantly different from prior to the turn. The shorter participants showed a trend of greater lateral movement than the taller. No shoulder belt slip-off occurred. For more than 95%, their head remained within the head-restraint width. The belt-tensioning did not influence the lateral movement, however the belt-tensioning perception deviated between individuals.

The frequent occurrence of non-nominal sitting postures, unlike crash test dummy postures in standardised testing, motivates more studies of this kind, gaining further understanding of the representativity of standardised tests, as well as real-world occupant protection.