An infrastructure system includes at least one sensor, a transceiver, and a computer communicatively coupled to the at least one sensor and to the transceiver. The computer is programmed to receive data from the at least one sensor indicating respective locations and motions of objects in an environment surrounding the at least one sensor; in response to one of (a) the data from the at least one sensor or (b) a request from a user, generate a virtual traffic marker at a first location in the environment; and instruct the transceiver to broadcast the virtual traffic marker to vehicles in the environment. The first location is based on the data from the at least one sensor, and the virtual traffic marker is data including the first location and traffic instructions corresponding to the first location.