A public entity is liable for injury caused by a condition of its property if the plaintiff establishes that the property was in dangerous condition at the time of the injury, that the injury was proximately caused by the dangerous condition, that the dangerous condition created a reasonably foreseeable risk of the kind of injury which was incurred, and that either:
Nothing in this section shall be construed to impose liability upon a public entity for a dangerous condition of its public property if the action the entity took to protect against the condition or the failure to take such action was not palpably unreasonable.
N.J.S. § 59:4-2