Mark Webber has called for changes to be made to the Drag Reduction System introduced into F1 for the 2011 season.

The system was brought in in an effort to increase overtaking, with drivers able to open a flat on their rear wing in order to boost their speed and try and to get ahead of the car in front.

While drivers can only use the system in a certain zone during race day, there are no restrictions in either practice or qualifying, with drivers able to use DRS whenever they like in an effort to gain time.

Although he admits the system has largely been a success on race day, Webber said that he felt changes should be made earlier in the weekend to prevent drivers having unlimited usage in practice and qualifying.

"At the moment, in the race you can only use the DRS in the designated zones - and then only if you are within a second of the car in front at the 'detection point'," the Red Bull driver wrote in his latest BBC column. "But in practice and qualifying you can use it whenever you like. That has led to a few incidents this year where people have gone off because they were pushing the boundaries of using the DRS.

"Renault's Bruno Senna had a crash in Suzuka, I had one on Friday in Hungary, and one of my team-mate Sebastian Vettel's practice crashes was caused by that, too.

"So the drivers are almost unanimous that they would prefer the use of DRS outside of a race to be limited - to just the DRS zone and perhaps a couple of key straights, plus a restriction on the point at which you deploy it so you're not too close to the exit of a corner."

Webber added that there have been times this season when the system hasn't worked perfectly, but said that DRS could now be refined for 2012 to ensure it works better next season.

"We are approaching each race this year 'blind', so inevitably there is a bit of trial and error involved, along with a lot of science," he said. "Inevitably, there have been some races where overtaking has been a bit too easy, such as China, Belgium and Turkey, others where it has still been too hard, such as Valencia, Barcelona and Korea, and others where it has been bang on. That's to be expected.

"It is a difficult subject to get right - and I'm sure with all the information gathered this season, it will be a lot closer to perfect next season.

"DRS is a controversial issue, not least because a lot of it depends on your point of view. Some people will like to see cars passing and re-passing all the time. NASCAR stock-car racing in America is founded on that. But for some who have a more purist point of view about F1 - like me - overtaking should mean more than that.

"They've done a good job so far and I'm sure the teams and the FIA will get the balance a bit better at some of the tracks next year."