To facilitate vehicle coverage for millimeter-wave applications, this communication presents a low-cost, wideband tilted-beam antenna. A novel design is proposed in which a slot antenna is both directly excited and electromagnetically coupled to a monopole array. This slot-monopole configuration is inherently robust against substrate losses, enabling low-cost fabrication while maintaining high realized gain and compact size. Furthermore, the slot-fed structure effectively excites multiple resonant modes within the monopole array, resulting in a significantly enhanced bandwidth. Experimental results demonstrate that the antenna achieves a -10-dB impedance bandwidth of over 76.5% (20-44.78 GHz) and a peak realized gain of 6.1 dBi.