Note the North Atlantic portion of the screen.
Typically, traffic only goes west to east for the early morning originators out of the eastern seaboard on their way to Europe.
Traffic inbound from Europe flies in much later in the day, all the way up to the redeye arrivals into our east coast.
That's how they separate traffic in this region of the world; specific time frames go east, times other than this go west.
There is no radar coverage over much of the North Atlantic. The airplanes fly tightly specified geographic tracks and altitudes, and they maintain a mach number as well as using GPS and datalink to tell air traffic controllers where they are.
If you aren't flying within the specified directional time frame, you can't fly on those navigation tracks or altitudes. You have to fly above or below them, or on a geographically separate course.
The system works well. No mid-air collisions over the Atlantic, but lots of traffic density.
v/r, N-A