1. IN A TRAM OF THE NATURE HAVING A CIRCULATING TRACTION ROPE SUPPORTED BY PLURAL TOWERS WITH DEPENDING CARRIERS SUPPORTED FOR MOTION BY SAID TRACTION ROPE, A CARRIER SWAY INDICATOR OF THE NATURE AFORESAID, COMPRISING, IN COMBINATION: PAIRED OPPOSED MOUNTING BRACKETS STRUCTURALLY CARRIED BY ADJACENT TRAM TOWERS SO THAT A LINE PASSING THERETHROUGH IS SUBSTANTIALLY TANGENT TO THE LATERAL LIMIT OF TRAVEL OF TRAM CARRIER AT AT LEAST SOME POINT THEREON BUT NO PART OF SAID LINE IS WITHIN THE NORMAL COURSE OF TRAVEL OF SAID TRAM CARRIER; A LIGHT SOURCE, CARRIED BY ONE OF SAID MOUNTING STRUCTURES, DIRECTING A DISCERNIBLE CONE OF LIGHT TO SAID OTHER MOUNTING STRUCTURE; A PHOTOELECTRIC CELL CARRIED BY SAID OTHER MOUNTING STRUCTURE ADAPTED TO OPERATIVELY RECEIVE AFORESAID CONE OF LIGHT TRANSMITTED THERETO BY AFORESAID LIGHT SOURCE; AND ELECTRICAL CIRCUITRY COMMUNICATING WITH SAID PHOTOELECTRIC DEVICE TO ANNUNCIATE UPON INTERRUPTION OF THE LIGHT BEAM BETWEEN SAID LIGHT AND SAID PHOTOELECTRIC CELL.