The options for high speed corridors are either upgrade and strengthen the existing high density traffic corridors to make them fit for high speeds and introduction of tilting trains on existing corridors or to build new dedicated lines for high speed traffic by separating them from incompatible services. This proposition is prohibitively costly and may not be relevant in the Indian context even upgrading of existing rail infrastructure to high speed corridor throws enormous challenges for civil engineers can be a good option. The travel time is the governing criteria for determining the commercial success of high speed corridors. The major factors determining the travel time are alignment and grades, acceleration/deceleration, stations and station spacing, track, structures and Level crossings.cheaper by the dozen dvd download last supper the download free