https://www.reuters.com/article/us-musk-tunnel/elon-musk-brings-high-tech-charm-offensive-to-los-angeles-tunnel-plan-idUSKCN1IJ02V >Billionaire entrepreneur Elon Musk promised a cheering crowd on Thursday that his controversial dream of burrowing a high-speed network of "personalized mass transit" tunnels under Los Angeles could be achieved without disturbance or noise at the surface.