Systems and methods are provided for improved traffic flow reporting (e.g., system bandwidth conservation and timely traffic flow updates) using in-vehicle devices, service hub, and communications system for transmitting aggregated traffic flow data to the vehicles. In-vehicle devices store data relating to monitored segments of roadways (e.g., segment identifiers or location codes and designated range(s) of speed), and send messages to the hub when current vehicle speed is not within a selected range designated for the current segment of roadway where the vehicle is located. Vehicles can be configured to send messages based on various criteria. A selected vehicle or group of vehicles can be commanded to send a message to the hub. The hub provides updated traffic flow data based on the messages to the communications system for transmission to the vehicles.