The reason I asked is because these places are so well connected by the rail network, and in the winter, conditions can be hit-or-miss. Someone mentioned the pileups above, totally true.
See, for example, this incident just two years ago:
The biggest pile-up in Czech history happened on Thursday after one of the country’s busiest motorways, the D1, was blocked by more than a hundred vehicles. They crashed due to heavy snowfall. The massive pile-up trapped around 20,000 people in their cars and rescue workers consider it a miracle that nobody was killed. Still, it took more than 12 hours to clear the motorway so that people could get home.
http://www.radio.cz/en/section/curra...-czech-history
Five days later:
A near 60 vehicle pile-up in heavy snow on Austria's main east-west highway causes one death with six injuries.
Obviously you're free to do as you wish, including being dismissive and rude to those trying to give you good advice. Two days in each of these places isn't enough to see or do much of anything except see the main tourist sites. And if you're driving, one incident (even one that doesn't directly involve you), can throw off the entire plan.