A new design approach of dual-band polarization and pattern diversity antenna for vehicle communications is presented. This antenna consists of three essential parts: monopole array, swastika-shaped gap-coupled patch, and customized L-shaped driven dipole. First, the monopole array composed of four monopoles beneath the patch is excited by the dipole-induced patch mode of the swastika-shaped gap-coupled patch so as to realize a bidirectional beam in the upper band. Second, the swastika-shaped gap-coupled patch is reused as the main radiator of the lower band to achieve wideband broadside right-handed circular polarization (RHCP) radiation, which is excited by a pair of customized parallel-lines-fed L-shaped driven dipoles. Finally, two short-circuited branches are etched in the long arm of the L-shaped driven dipole, bringing in the out-of-band suppression improvement between the lower and upper bands. In order to verify the developed design method, a dual-band antenna with different polarization and radiation properties over two bands was designed, fabricated, and tested. Measured results indicate that the developed antenna with a compact transversal size of $0.36\lambda {0} \times 0.36\lambda {0}$ radiates broadside RHCP electromagnetic wave in 3.55-4.25 GHz and bidirectional vertical polarization (VP) in 5.62-6.38 GHz, which covers C-band and dedicated short-range communications (DSRC)-band, and especially serves as a promising candidate for applications in both vehicle-to-satellite (V2S) and vehicle-to-everything (V2X) communications.