To artificially spice up racing the FIA has decided to have two stretches of racing tarmac instead of one for the DRS system to be used.  The DRS system means that the drag on the rear wing is reduced by opening a flap and this aids in overtaking.  So far only one stretch on the track is open for DRS enabling.  But in Canada and Valencia this can be done in two places.  The FIA has also said that the DRS cannot be used in the tunnel and at Eau Rouge in Monaco for reasons of safety.