The Flintstones came out in the early to mid 1960s, right at what you might call the height of the postwar freeway and suburban building boom. One of the most famous jokes from the show is that everybody gets around in "cars" powered by running.
Of course, it's absurd to get around this way. Fred could have made more progress ditching all that dead weight and running. I don't mean to analyze this too seriously, but I do think it's interesting that America was so dependent on cars even then, that we would project them onto an image of the "past" for comic effect. And onto the "future" for that matter (i.e. in The Jetsons, another early 1960s cartoon).
The more I think about it, the best joke of the whole show is the idea that people could have lived in a suburb, like the Flintstones and the Rubbles do, without fossil fuels.
Indeed, given that oil will start to run out and become prohibitively expensive, the town of Bedrock may be more future than past for us, if we don't come up with a more sustainable land use and transportation paradigm.