Future cars will constantly sense the environment and interchange information with their surrounding in order to successfully choose routes, avoid hazards, and comply with traffic regulations. These vehicles will be equipped with multiple sensors, including automotive radar, as well as wireless communications capabilities. The similarity in hardware and signal processing of automotive radar and wireless communications motivates designing these functionalities in a joint manner. Such dual function radar-communications (DFRC) designs are the focus of a large body of recent works. These joint designs lead to substantial gains in size, cost, power consumption, and performance, making them especially important for vehicular applications, where both the radar and communications operate in similar ranges. This paper reviews a wide variety of existing DFRC strategies and their relevance to automotive systems. We discuss the pros and cons of current methods, mapping them in the context of vehicular application, and present the main challenges and possible research directions.