Red Bull has become the latest Formula 1 team to run a passive DRS. Sebastian Vettel tried the device out on the second day of testing at Barcelona on Friday.
A number of teams are evaluating using the concept, which helps stall the rear wing for a straight-line speed boost beyond that available from normal DRS.
The passive systems are triggered when the car reaches a certain speed. They have proved tricky to get working properly, primarily because they do not necessarily get deactivated at the same speed at which they come into play. That means drivers could find themselves without essential rear wing downforce for high-speed corners if the device has not been set up properly.
Sauber, Mercedes and Lotus have all tried the system so far, but none appears to be confident enough with it yet to be able to run it from the first race.
Lotus technical director James Allison said at Barcelona this week that his team was getting more comfortable with the system it is trying, but was not yet ready to commit to racing it.
"It's a very difficult thing to get right," he said. "It's a passive device, so the strength of the switch isn't very high.
"It's a case of making the switch clean, repeatable, and strong enough to trip the wing. But you also want a wing that is able to be nice and robust when not being tripped. It's a very delicate see-saw to keep it balanced."
Red Bull's technical chief Adrian Newey said at the launch of this year's RB9 that his team was continuing its development of the idea.
"It's a very interesting area, and it's there to be explored," he said. "Deriving lap time benefit, or more importantly points benefit, out of it, is more difficult."