(1m)   The operator of a motor vehicle shall not follow another vehicle more closely than is reasonable and prudent, having due regard for the speed of such vehicle and the traffic upon and the condition of the highway.

   (2)   

      (a)    Upon a highway outside a business or residence district, the operator of any motor truck with a gross weight of more than 10,000 pounds or of any motor vehicle which is drawing or towing another vehicle where the combined gross weight is more than 10,000 pounds shall do all of the following:

         1.    Keep the vehicle he or she is operating at a distance of not less than 500 feet to the rear of any vehicle immediately preceding it, being driven in the same direction.

         2.    Leave sufficient space so that an overtaking vehicle may enter and occupy such space without danger.

      (b)    This subsection does not apply upon any lane especially designated for use by motor trucks or by truck tractor-semitrailer or tractor-trailer units nor does it apply when overtaking and passing another vehicle, but the fact that the operator of any vehicle or combination of vehicles mentioned in this subsection follows the preceding vehicle more closely than 500 feet for one mile or more or follows more closely than 500 feet when the preceding vehicle is moving at the maximum speed then and there permissible for such following vehicle is prima facie evidence that the operator of such following vehicle is violating this subsection.

      (c)    This subsection does not apply to an operator of vehicle in a platoon other than the lead vehicle.