Apparently at Winterthur you can drive on to the grounds but you better not arrive by bicycle. The estate has “temporarily” banned bicycles to keep them from using the pedestrian paths.
Ironically there is a webpage on the Winterthur website that talks about bicycle advocacy in the 19th Century:
“Not just a short-lived fad, bicycling brought about many long-term advantages, among them better roads. The lobbying efforts of bicycle leagues had a profound impact on America’s burgeoning transportation system, in the end greatly benefiting the next advance in transport: the automobile.”