Up until about 1970, there were no codes or standards for the overall strength requirements of a transit vehicle carbody that were fully based in engineering principles. Beginning about that time, the usual requirement in specifications became that the carbody needed to accept, without structural failure, a longitudinal static “buff load” equal to two times its own mass.
This was known as the “2-g standard,” although it was never actually codified as a mandatory requirement except in the State of California.[5] Under the 2-g standard, if the vehicle weighed 125,000 pounds [556 kilonewtons] it needed to have a minimum buff strength of 250,000 pounds [1,112 kilonewtons].
Naturally, the addition of more steel to make the carbody stronger also increased its mass, with the result that new transit cars were much heavier than their predecessors. This extra weight had impacts on power consumption, structure design, and track design.
