Abstract: In many contexts, vehicles navigate routes while providing a service on behalf of a service provider, and with the assistance of global positioning systems (GPS) for navigation, routing, and/or vehicle tracking. In addition to identifying the location of the vehicle, devices with integrated GPS may also identify a population density (e.g., of individuals, cyclists, or other vehicles) within a vicinity of a location of the vehicle, which may caution a driver of high-population-density areas; may be used to assess a risk of the vehicle while navigating the route, and/or to suggest alternative routes; and/or to count the people who observe the vehicle navigating the route while performing the service. The GPS and/or population density estimator (e.g., a camera) are integrated with a car topper that is mounted atop the vehicle with a display that identifies the service, and optionally with a reversible mounting attachment and/or an integrated high-gain antenna.