I would also like to add, it is a lack of hakoras hatov to decide a person doesn’t have the right intentions when shoveling the snow in front of their property. And right intentions or not, we must have hakoras hatov to those who do shovel.
There is many many people who were injured in the past month, some seriously. So anyone who shovels is doing all of us a favor, making it easier for us and our loved ones to get places safely. And putting up signs of warnings is pretty much nonsense.