Many, but not all, diesel trains use only friction brakes (as do cars and trucks) to slow or stop the train. This wears the discs and pads, introducing particulates into the atmosphere. Electric trains predominantly use the motors in regeneration mode to slow the train, producing almost zero particulates. The technology does not yet exist to stop the train completely. Using this technology would improve the health of the nation but in particular for people who live closer to the railway. In addition, regenerative braking saves energy and is more efficient and thus helps the low-carbon economy. Diesel trains also generate soot and particulates from the engines, often clearly visible in the air. Electrification vastly reduces or even eliminates this problem, thus bringing cleaner and healthier air.