A mobile device can obtain wireless network signal strength map data that indicates, for various nearby geographical regions, the wireless network signal strength in each such region. A mobile device can transmit that data to a vehicular navigation system responsible for automatically selecting a high-quality route of vehicular travel between a specified source and destination. The system can take the wireless network signal map data into account when selecting that route. When selecting from among multiple different routes of vehicular travel between a specified source and destination, the system may employ an algorithm that considers wireless network signal strengths along those routes, in addition to the other factors. Consequently, the system can select a longer route having better signal strength over a shorter route having worse signal strength. The system can present the selected route within a set of suggested routes, potentially along with reasons for each route's suggestion.