A fleet of vehicles (“connected vehicles”) are equipped to wirelessly transmit data in real time, the data including at least an identifier of the vehicle, a GPS location, and a timestamp. Preferably, messages may be sent from the vehicles approximately once per second. This “probe data” from operating vehicles is analyzed to assemble vehicle operation data over a collection period of say, a few weeks. The data is analyzed for a specific signalized intersection. In an embodiment, a preferred process is to leverage the connected vehicle probe data to figure out the traffic volume for a target time period and location, and then optimize the corresponding timing plan for that time period for the subject signal/lane/phase. Target time periods may be on the order of 15 minutes, 30 minutes or an hour, although the exact time period is not critical.