What is the Protection of Investment Rule?
The law contemplates that the first licensee will be protected in his investment and will not be subjected to a ruinous competition. So long as an operator under a prior license complies with its terms and conditions and the reasonable rules and regulations for its operation, and meets the reasonable demands of the public, it will be protected rather than destroy its investment by the granting of the second license to another person for the same thing over the same route of travel. Note: The "prior operator" and "protection of investment" rules cannot take precedence over the convenience of the public. (Martires Ereno Co. v. Public Service Commission, G.R. No. L-25962, Sept. 30, 1975)