In a RAC drawing of a graph, vertices are represented by points in the plane,
adjacent vertices are connected by line segments, and crossings must form right
angles. Graphs that admit such drawings are RAC graphs. RAC graphs are
beyond-planar graphs and have been studied extensively. In particular, it is
known that a RAC graph with n vertices has at most 4n - 10 edges.
We introduce a superclass of RAC graphs, which we call arc-RAC graphs. A
graph is arc-RAC if it admits a drawing where edges are represented by circular
arcs and crossings form right angles. We provide a Tur\'an-type result showing
that an arc-RAC graph with n vertices has at most 14n - 12 edges and that there
are n-vertex arc-RAC graphs with 4.5n - o(n) edges