10.2c(iii) is pretty clear that this use is explicitly allowed:
"you may use the Google Maps API(s) to track assets such as cars, buses or other vehicles, as long as your tracking application is made available to the public without charge. For example, you may offer a free, public Maps API Implementation that displays real-time public transit or other transportation status information.)"
"you may use the Google Maps API(s) to track assets such as cars, buses or other vehicles, as long as your tracking application is made available to the public without charge. For example, you may offer a free, public Maps API Implementation that displays real-time public transit or other transportation status information.)"