Acting on the Amtrak-Conrail collision near Baltimore last winter, the Transportation Department ordered all trains operating between Washington and Boston to be equipped with automatic stopping devices. The Transportation Department said the safety devices, which would automatically stop or slow a train even if an engineer fails to obey a signal, must be installed by July 1, 1990. Amtrak trains operating in the Northeast Corridor already are equipped with such devices but the Conrail freight line and other trains sharing the tracks are not. The collision at Chase, Md., killed 16 people and injured 176, and occurred after the Conrail crew disregarded several warning devices, including a stop sign. The railroads generally have resisted installing the devices on freight locomotives, arguing that the automatic brakes under some circumstances could activate and cause a derailment.