Amazon has a new cure for long supermarket lines: a smart shopping cart. The cart, which Amazon unveiled on Tuesday, uses cameras, sensors and a scale to automatically detect what shoppers drop in. It keeps a tally and then charges their Amazon account when they leave the store. No cashier is needed. It’s the latest attempt by Amazon to shake up the supermarket industry and offer a solution to long checkout lines. The online shopping giant opened a cashier-less supermarket in Seattle that uses cameras and sensors in the ceiling to track what shoppers grab and charge them as they leave. Amazon.com Inc. also has roughly 25 cashier-less convenience stores with similar technology. The cart, called Amazon Dash Cart, will first show up at a new Los Angeles supermarket Amazon is opening later this year. The store will have cashiers, but Amazon said it wanted to give shoppers a way to bypass any lines. In the future, it could be used at Amazon´s Whole Foods grocery chain or other stores, if Amazon sells the technology, but there are no plans for either right now.