At-grade pedestrian crossings (AKA Zebra Crossings) leave the potential for high-speed crashes to occur. The Crash Reduction Factor/Crash Modification Factor for these facilities varies wildly amongst studies from around the world from a reduction in pedestrian safety to a modest improvement.
Raised pedestrian crossings on the other hand are well proven to have big benefits for pedestrian safety. The total number of pedestrian casualty crashes reduces by 73% (Makwasha and Turner 2015) with the installation of a raised pedestrian crossing (called a Wombat Crossing in Australia).