**6. Interface pressure**

The overall seat discomfort is influenced by both dynamic and static seat characteristics. These two factors are firmly connected, the importance of one depends on the influence of the other. In low or absent vibration, discomfort evaluation depends mostly on the static seat characteristics. On the other hand, dynamic features dominated discomfort evaluation when vibration magnitude increases. Therefore, it is essential to consider both static and dynamic seat characteristics when evaluating passengers' comfort. Interface pressure is commonly used as a static comfort evaluation technique [63, 64].

When a passenger sits, the pressure at the interface between the seat and the user's buttocks varies over the seat surface area. This pressure variation defines the "average pressure", representing the mean pressure induced on the seat surface. On the other hand, some pressure is concentrated around the ischial tuberosities leading to pressure peaks [64, 65]. A maximum 32 mmHg threshold should not be exceeded. This value corresponds to the capillary pressure value, and above that the pressure is considered harmful as it can obstruct the capillaries, restricting blood circulation and, consequently, result in a deprivation of oxygen to the tissues, causing discomfort [63, 66– 68]. The ideal foam equally distributes pressure on the seat surface.

After evaluating the dynamic seat characteristics of the Pendolino train, the static conditions were assessed by measuring its interface pressure. Experiments run with the same conditions (seats and subjects) as the transmissibility tests. The interface pressure was recorded using a CONFORMat sensor (from TekScan) for 10 minutes for each individual, and maximum pressure was recorded. **Figure 5** illustrates the

**Figure 5.** *Pressure distribution: (a) comfort seat, b) touristic seat.*

pressure distribution for Pendolino seats regarding M2 subjects. Similar tendencies were observed for all individuals.

Maximum pressure of 32 and 37 mmHg were found for the comfort and touristic seats, respectively. Those pressures correspond to the discomfort threshold; thus, passengers may feel discomfort. Apart from the ischial tuberosities, the pressure was equally distributed on the seat surface.
