In this work a theoretical and experimental investigation analyzing VHF/UHF radio wave propagation in a suburban environment with a grid-type street plan is presented for the purpose of personal communication services prediction. A waveguide with randomly distributed gaps (slits) between the sides of buildings is considered as a model of straight streets with two- and three-story buildings. The average field intensity and path loss at the street level, taking into account the reflection from the ground, multireflection, and diffraction from the walls and building edges, are investigated in line-of-sight (LOS) conditions using a new three-dimensional multislit waveguide model. This model gives good agreement with the two-rays model and with an experimentally found law of field intensity attenuation at the street level with high and low building density up to 1–2 km from the source.