Section 391. Rates of toll on motor vehicles

Where a different rate is not
  otherwise  prescribed  or  permitted  by  law, any person or corporation
  maintaining a plank road, turnpike road or  bridge  and  authorized,  or
  which shall be hereafter authorized, to receive tolls for the passage of
  motor  vehicles over the same, may charge and receive for each and every
  motor vehicle propelled by any power other than  animal  power,  passing
  over  the same, a toll rate not greater than the maximum rate allowed by
  law to be charged and received for the passage of a vehicle  drawn  over
  such  road  or  bridge  by  two  animals,  provided  that for such motor
  vehicles designed to carry only two persons the rate of toll charged  or
  received  shall not exceed the maximum rate allowed by law to be charged
  and received for the passage of  a  vehicle  drawn  over  such  road  or
  bridge, without a load, by a single animal.