@CNN: Positive train control, or PTC, can automatically slow down and stop a train if it senses the locomotive is going too fast or could get into an accident. Could it have prevented the Amtrak crash in South Carolina? https://t.co/CeJ39AwIbP https://t.co/enfW974Vr9

@CNN: Positive train control, or PTC, can automatically slow down and stop a train if it senses the locomotive is going too fast or could get into an accident. Could it have prevented the Amtrak crash in South Carolina? https://t.co/CeJ39AwIbP https://t.co/enfW974Vr9