Animal Crossing Considerations Animals were here before man, and have certain rights to our earth, rights like the right to migrate to birthing and feeding areas, rights of passage over lands that are passable, and rights to not be denied food and shelter. The BorderTransportationSystem is designed to prevent unauthorized crossings by humans of all sizes from a baby crawling to a massive giant scaling a fence.  At the same time we are attempting to stop human crossings, we still must allow certain animal crossings.  The following are some ideas and tentative solutions, solutions that have been built and proven, and some alternative ideas that as of yet have not been built and proven. Index of ... Bird and Flying Insect routes Domestic Animal Tunnels Drug only passage Environmental Species Large Animals Mid-size Animals Small Animal pipelines