Whenever any railroad or public highway will be beneficially affected by the construction of any improvement or improvements in such district, it shall be the duty of the commissioners appointed to classify and assess benefits to determine and return in their report the amount of the benefit to such railroad or highway, and notice shall be served as to such railroad upon its nearest station agent, as provided in case of an individual property owner; and as to a highway, notice shall be served upon the county mayor, as in case of an individual property owner. When such special assessments have been approved and fixed by the county court as to such railroad, it shall be a debt due personally from the railroad company, and, unless the same is paid by the railroad company as special assessment, it may be collected in the name of the county in any court having jurisdiction; and as to a highway, such assessment shall be paid by the county out of the general county fund or highway tax fund, such assessments to be paid into the fund of such district.