In 1932, Stalin was obsessed with getting money to fund the big war he was planning. As part of his money-making activities that year, he was not only starving 8,000,000 Ukrainians to death but also trying to attract Western tourists with posters like this one:
It looks like cars were allowed onto the Red Square back then but I don’t know if it’s true or part of poetic licence. Today they aren’t, of course. Neither are pedestrians unless there is a special dispensation.