A contraflow system is where two cars meet at a junction either going left or right
crontraflow is bad
You will typically see a contraflow bus and cycle lane on one-way streets that allow buses and bicycles to travel in the opposite direction of the regular flow of traffic. This setup helps improve transportation efficiency and safety for cyclists and bus passengers.
These terms are usually used in conjuction with fluid-fluid heat exchangers. In both cases, the two fluids in the exchanger are moving in parallel flowpaths with each other. In contraflow, the fluids move in opposite directions along those paths, so the two inlets are on opposite ends of the exchanger. In parallel flow, the fluids move in the same direction, so the inlets are on the same end.