Minecraft wiki entry for Cobweb, associated text: A minecart with no players in it takes about 9 seconds to fall through a cobweb if a rail is placed directly under the cobweb, however, if there is air between the cobweb and the rail, the minecart takes about 34 seconds to fall. Every extra cobweb added gives an additional 25 seconds of falling time. Players are unaffected by cobwebs when in a minecart unless they come into direct contact.