When DRSThe Drag Reduction System (DRS), is designed to do exactly what it says, reduce drag, resulting in the recipient gaining... There's more... is active and a number of consecutive cars are all within one second of each other they all, apart from the lead car, get the benefit of activating DRS and gain an additional 13 – 15kph through the DRS zones.
The effect of multiple cars racing this close under DRS is refered to as a DRS train.