“…More recently, several other classes have been suggested (e.g., [6,11]), also motivated by cognitive experiments [32,37] indicating that the absence of certain types of crossings helps in improving the readability of a drawing; for a survey, refer to [24]. Some of the most studied are: (i) fan-planar graphs, in which no edge can be crossed by two independent edges or by two adjacent edges from different directions [12,13,33], (ii) fan-crossing free graphs, in which no edge can be crossed by two adjacent edges [16,19], (iii) gap-planar graphs, in which each crossing is assigned to one of its two involved edges, such that each edge can be assigned at most one crossing [11], and (iv) RAC graphs, in which edge crossings occur only at right angles [22,23,25]; see Figs. 1c-1e.…”