Part of the justification for the insane expense of the interstate highway system (besides the dubious defense benefits) was that it would act as a check on usurious rates by the railroads. Yes, we could just regulate or nationalize the railroads (that the public largely created via huge land giveaways and other benefits) but it's more American to counter the flaws of one big business welfare program with another: subsidizing auto infrastructure as a giveaway to Detroit and the oil companies.