Section 137. The department may, on the application of a railroad corporation whose railroad crosses another railroad at the same level, after notice to the parties and a hearing, authorize the applicant at its own expense, to establish and maintain a system of interlocking or automatic signals at any crossing of said railroad, and to erect and maintain the necessary wires, rods, signal posts and signals, in such manner as the department shall prescribe. Such corporation, after the system has been established and approved in writing by the department, shall be exempt as to such crossing from the requirements of section one hundred and thirty-five so long as the department continues its approval. Upon payment to such corporation by the corporation owning or operating the other railroad at such crossing of so much of the cost of establishing such system of signals as, upon petition of the latter corporation and a hearing, is awarded by the department, both railroad corporations shall, as to that crossing, be exempted from the requirements of said section. Until such payment the latter corporation shall semi-annually contribute toward the expense of operating said signals an amount equal to the cost to it of operating the signals used by it at said crossing before the establishment of the signals herein provided for. After the payment of such award, the expense of maintaining and operating such system of signals shall be borne by the two railroad corporations according to the proportions fixed by the award for paying the original cost of the signals. So much of the award as relates to the cost of maintaining and operating said signals may, at the request of either party, be revised at the expiration of five years from the original award or from any revision thereof.