Since when have most tractors and trailers manufactured for use in combination been required to have anti-lock braking systems (ABS)?

Pick an answer

1. ABS became required only after 2020
2. Since federal requirements phased in ABS for new tractors, trailers, and buses starting in the 1990s
3. It has been mandatory since the very first diesel tractors were built
4. ABS has always been standard equipment on every commercial vehicle ever built, going back decades before 1990

Correct!

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