https://www.reuters.com/article/us-musk-tunnel/elon-musk-brings-technology-charm-offensive-to-los-angeles-tunnel-plan-idUSKCN1IJ02V >Billionaire entrepreneur Elon Musk is bringing his technology charm offensive to an attempt at digging a tunnel beneath part of Los Angeles to test designs for a high-speed subterranean transportation network he envisions for the city.