The landlord is responsible for keeping the rental premises, including any provided parking safe (such as by salting it), unless there is a single tenant who leases the *entire* space (e.g. the whole building and the parking area). When a single tenant leases everything, that tenant is responsible for this sort of upkeep (unless there is a lease still making it the landlord's responsibility), the way that if someone leases a single family home with a garage, he or she must do his/her own shoveling, salting, etc. But with multi-tenant units, the landlord remains responsible for the "common areas," like a parking ramp; and if the landlord fails in his responsibility, he can become liable for the costs or damage that his failure to keep those areas safe causes.