The future exploitation of cooperative vehicular services in urban environments, generally characterized by challenging propagation conditions, will require an efficient deployment of roadside units. This article presents the results of an extensive field testing campaign aimed at analyzing the impact of urban characteristics, RSU deployment conditions, and communication settings on the quality of IEEE 802.11p vehicle-to-infrastructure communications. The reported results show that the streets' layout, urban environment, traffic density, presence of heavy vehicles, trees, and terrain elevation have an effect on V2I communications, and should be taken into account to adequately deploy and configure urban RSUs.