The driver of a motor vehicle may not follow another vehicle more closely than is reasonable and prudent, having due regard for the speed of the other vehicle and of the traffic on and the condition of the highway. Subject to the provisions of subsection (d) of this section, whenever conditions permit, the driver of every truck, while traveling on a roadway outside of a business district or a residential district and following any other truck or any other motor vehicle towing another vehicle, shall leave enough space so that an overtaking vehicle may enter and occupy the space without danger. Subject to the provisions of subsection (d) of this section, whenever conditions permit, the driver of every motor vehicle towing another vehicle, while traveling on a roadway outside of a business district or a residential district and following any other truck or any other motor vehicle towing another vehicle, shall leave enough space so that an overtaking vehicle may enter and occupy the space without danger. A truck or a motor vehicle towing another vehicle may overtake and pass any other vehicle or combination of vehicles. This subsection does not apply to a funeral procession. A motor vehicle being driven on a roadway outside of a business district or a residential district in a caravan or motorcade, whether or not towing another vehicle, shall be driven to allow enough space between each two vehicles or combination of vehicles so that any other vehicle may enter and occupy the space without danger. Notwithstanding any other provision of this section, the driver of a nonlead truck in a group of trucks may travel without leaving enough space so that an overtaking vehicle may enter and occupy the space between the trucks if the trucks are: Traveling in a unified manner with electronically coordinated speed and braking systems; and Operating in a reasonable and prudent manner with due regard for the speed of any other vehicles and of the traffic on and the condition of the highway. The Administration shall adopt regulations to carry out this subsection, including regulations governing: The number of trucks allowed in a group operating in a unified manner; The roadway conditions under which trucks may be operated in a unified manner; The required submission of a plan of operation by a person operating a truck in a unified manner; and The submission of any other information as required by the Administration for the purpose of evaluating safety issues relevant to the operation of trucks in a unified manner.