This is BAD advice on cars that have power steering or power brakes, as most cars today do.
Definitely be careful not to lock your steering.
But at 4 miles per hour, on a straight highway, the power steering isn't a problem. If you don't have the strength to put the brakes on without power, definitely don't do this. It isn't easy -- I should have said that.
If your emergency brake works, it is another way to control your speed without engine power. But I would only mess with this if I had another 50 miles to go and was down to my last gallon of gas.
I don't think you should have to do this, the roads should clear up.
I'll admit that I wouldn't do this myself, but I wouldn't have to, because both my cars are Priuses, and they shut down their engines when stopped -- another advantage of hybrids, which will get you 30 mpg in stop-and-go traffic, (so long as you don't run the AC full blast).