Low-power sensing and communication technologies have evolved to the point where it is feasible to install intelligent, wirelessly-connected sensors pervasively on roadways to enable precise, real-time monitoring of traffic flows. Efficient operation of the sensing, computing and communications subsystems in these devices offers the possibility of battery lifetimes comparable to replacement cycles for normal raised pavement markers, making install-and-forget sensing a practical reality. But such unobtrusive mounting on the road surface brings with it an inherent problem. Data signals sent from the wireless devices in these sensors suffer from the effect of ground reflection which distort the antenna’s pattern. We explore this fundamental problem and its possible solutions from first principles. We offer an approach for antenna / enclosure co-design that yields a 6 dB gain improvement over a simple dipole antenna.