Is it illegal to push a car with another car?

It depends on local laws and regulations, but in many areas, using one vehicle to push another in traffic is legal only in emergencies with necessary safety precautions taken. Some regions may require hazard lights to be turned on, a safe following distance between the cars, and a visible warning sign on the rear of the towing vehicle, such as a red flag or reflective sign. Always consult local traffic laws before employing this practice.