Regular pool, open two lanes, swim laps (up one lane, down the other). It's done with two lanes, so there is enough room to pass. I've seen it done this way several places.
I’m confused as to what you are suggesting here? Normally you swim right side of the lane and turn going back on the “left side”, with room to pass on the inside unless the lane is filled with two many people. What does using two lanes add, except ruining your turns?