As the L-4 bus, bound for Chevy Chase Circle began to pull away from a stop at 19th and K Streets NW in the rush hour Monday evening a would-be passenger who had been chasing it for a block down the sidewald ran up to its closed front door.

The driver refused to reopen the door to let him board, even though the bus had to stop for traffic signal.

So the frustrated passenger, a wool muffler pulled high around his reddened cheeks, stepped into the path of the bus and turned defiantly toward the driver. If he couldn't ride, he made it clear by his rigid stance, nobody else would.

Neither budget. Minutes went by. Frustrated passenger and foiled driver shouted at one another. Gwen Mitchler, a telephone operator for The Washington Post who was aboard the bus, looked out the back window and saw other buses lined up as far as she could see. Passengers in her bus looked impatiently at their watchers.

Finally, the driver of one of the driver of one of their backed-up buses dismounted and walked up to the defiant passenger and invited him into his vehicle - an express on the same Connecticut Avenue line. The passenger accepted.

Mrs. Mitchler said her own trip home, which oridinarily takes 15 to 18 minutes, took precisely 30 minutes that night.

Thomas S. Trimmer, Metro transportation director, said the driver of the halted but failed to report the incident, which he should have done, so he could not be immediately identified.

As for the driver failing to repoen the door for the passenger, Trimmer commented, "We expect our operators to excercise good judgement." Did this driver? Probably not, Trimmer said.