It is true that 146s/RJs are not fitted with thrust reversers-and braking is provided by 4 very efficient carbon brakes-even if only 3 are working it still stops well. There is also a lift dumper at the back which opens just before landing. The problem is that if there is snow on the runway doesnt matter how good the braking is the wheels wont grip. Prop driven aircraft (ATPs) can make a better job of it because the prop can provide some of the braking action that the wheel brakes might not be able to give in contaminated runway conditions. The secret is to keep the runway deiced which costs a fortune in spray and equipment and sometimes even with the best gear the airport authorities just have to wait untill the weather clears up a bit.