  A k-bend right-angle-crossing drawing or (k-bend RAC drawing}, for short) of
a graph is a polyline drawing where each edge has at most k bends and the
angles formed at the crossing points of the edges are 90 degrees. Accordingly,
a graph that admits a k-bend RAC drawing is referred to as k-bend
right-angle-crossing graph (or k-bend RAC, for short).
  In this paper, we continue the study of the maximum edge-density of 1-bend
RAC graphs. We show that an n-vertex 1-bend RAC graph cannot have more than
$5.5n-O(1)$ edges. We also demonstrate that there exist infinitely many
n-vertex 1-bend RAC graphs with exactly $5n-O(1)$ edges. Our results improve
both the previously known best upper bound of $6.5n-O(1)$ edges and the
corresponding lower bound of $4.5n-O(\sqrt{n})$ edges by Arikushi et al.
(Comput. Geom. 45(4), 169--177 (2012)).
