The FIA has lifted restrictions on the use of DRS when yellow flags are shown as part of its efforts to increase overtaking.
Prior to the Canadian Grand Prix, if a yellow flag is shown in any zone, then the drag-reduction system would have been globally deactivated across the entire track, meaning a driver would be unable to use it even if they weren't within the yellow zone.
As the FIA pushes to increase DRS use – in Canada they added a third DRS zone and have hinted at more in future races – they want to avoid drivers missing out on the extra performance it provides, particularly if they're locked in a close fight for position, and therefore won't now deactivate the system during the entire race weekend through practice, qualifying and the race.
However if a yellow flag is displayed within a DRS zone, then the onus will be on the driver to slow sufficiently – as they're already required to – without activating their DRS.
This was revealed in revised race notes issued ahead of the Canadian GP, where the usual section on DRS had been deleted.
Another contributing factor to the change is, as the FIA adds more zones, the complexity of the system increases and therefore makes it harder to deactivate only part of the system, which makes policing the use of DRS within a yellow zone very difficult and could lead to unfair penalties.
