IN THE FIRST STUDY, RESEARCHERS SYSTEMATICALLY OBSERVED BEHAVIOR OF PASSENGERS ON THREE SEPARATE RAPID TRANSIT LINES SELECTED FOR VARIATION IN PATRONS' RACIAL COMPOSITION AT MIDWEEK, NONRUSH HOUR TIMES. AN OBSERVATIONAL RECORDING SHEET WAS USED TO RECORD THE SEATING POSITION OF RIDERS, USE OF ANY OBJECTS TO MARK SEAT BARRIERS, RIDERS' CHARACTERISTICS, CONVERSATIONAL EXIT AND ENTRANCE BEHAVIOR, AND SCANNING BEHAVIOR. RESULTS INDICATED THAT MOST PASSENGERS SELECT A SINGLE SEAT WHEN ONE IS AVAILABLE, SELECT A SEATMATE WITH SIMILAR RACIAL CHARACTERISTICS, AND SCAN PASSENGERS ENTERING THE TRAIN BUT AVOID EYE CONTACT. RESEARCHERS OBSERVED THAT 11.8 PERCENT OF THE SEATED RIDERS OBSERVED ENGAGED IN SOME FORM OF BLOCKING (ERECTING BARRIERS SO THAT ANOTHER PASSENGER WILL NOT SELECT THE SEAT ADJACENT TO THEM, AND THAT BLOCKING PATTERNS DID NOT VARY ACCORDING TO RACE OR SEX. BLOCKING INCIDENCE WAS HEIGHTENED WHEN THE CARS PASSED THROUGH THREATENING AREAS, SUCH AS HIGH CRIME AREAS OF THE CITY. IN THE SECOND STUDY, RESEARCHERS INTERVIEWED 120 RIDERS ON SOCIAL BEHAVIOR AND PERCEPTION OF PERSONAL SAFETY WHILE RIDING THE TRANSIT SYSTEM. ONLY 17.5 PERCENT OF THE RIDERS FELT SAFE DURING THE ENTIRE TRIP, 55 PERCENT AVOIDED RIDING THE TRAIN DURING NIGHT HOURS, 34.2 PERCENT AVOIDED RIDING THE TRAIN THROUGH CERTAIN AREAS OF THE CITY, AND MOST PERSONS FELT MOST SAFE DURING THE WALK TO THE TRAIN STATION AND LEAST SAFE ON THE PLATFORM WAITING FOR THE TRAIN. OF THE PERSONS INTERVIEWED, 46.7 PERCENT INDICATED THAT THEY ATTEMPT TO SIT IN THE CAR WITH THE CONDUCTOR, 30.8 PERCENT ATTEMPT TO SIT ON A SINGLE SEAT, AND 57.5 PERCENT TRY TO AVOID CERTAIN TYPES OF PERSONS ON THE TRAIN, USUALLY INTOXICATED PERSONS, MEN, AND GROUPS OF BOYS. THE MAJORITY OF RESPONDENTS REPLIED THAT THEY FEEL CAPABLE OF HANDLING A THREAT SITUATION WHILE RIDING IN A CAR AND MOST OF THEM RESPOND TO SUCH A SITUATION BY DOING NOTHING. IMPLICATIONS ARE REVIEWED. THE QUESTIONNAIRE, TABULAR DATA, AND A BIBLIOGRAPHY ARE INCLUDED. (DAG)