If, as The Post reported Sept. 15, the National Transportation Safety Board has a draft report alleging that Metro's decision to use the B&O right-of-way for part of our Red Line was reached ''with little regard for the inherent safety problems," kindly warn them they are dead wrong about that. Regardless of what consultant reports on file contain, as one of the Metro directors who made that important decision, let me tell you what really happened.

The risk of inter-track friction resulting in passenger injury was very much on my mind and discussed with colleagues, but that risk had to be weighed against two other opposing ones:

Would the added cost of acquiring a separate right-of-way or tunneling become all that the highway lobby needed to kill Metrorail in Congress?

If not, would the residents of the affected corridor succeed in blocking that Red Line alignment?

Federal safety experts are not responsible for considering those other risks, but they should recognize that we were.

Considering the steady, rapid escalation of Metrorail construction cost estimates due to rampant inflation in the early '70s, which was constantly used against us, it was entirely possible that cost revisions such as the NSTB now seems to think we should have made would have effectively killed Metrorail in Congress. Remember that a federal financing share for the entire system was literally nip and tuck at that time.

Moreover, as for the neighborhoods that would have been adversely affected by such a separate right-of-way, considering what happened to the proposed center leg of I-95 through Brookland, it is highly likely (if not certain) that this entire Red Line segment would be at the same stage of development today as the Green Line at Fort Totten or beyond the Anacostia Station. The question we faced was how much safety risk must be assumed in order to obtain the desperately needed rapid rail transportation.

All modern transportation entails some safety risk. This must be balanced against the service to be provided. Every time a 747 takes off there is (to use the board's words against Metro) a ''potential for catastrophe'' if it crashes with hundreds aboard; but the safety board correctly balances this against the passenger miles between ''catastrophes'' and does not criticize. Despite two significant derailments in the CSX-Metro corridor, no one has even been hurt there yet.

After some 15 years, our balancing of risks in going with the B&O roadbed solution has been vindicated so far, and we pray that it will continue so. Of course, further efforts to reduce that risk to passengers would be most welcome, but it is simply revising history to say, in the board's draft report, that there was ''little regard'' for safety in reaching our decision. JOHN A. NEVIUS Washington