"A lack of communication of essential information" among various parties involved in the testing operations of Metro's new trains was responsible for the collision of two trains Sept. 11, a Metro safety committee has concluded.

The committee, composed of technical experts from the Metro staff, reached that conclusion after a long investigation of train control room tape recordings, computer logs and interviews.

What they found was a classic transportation accident: a series of little mistakes that, taken alone, would not have caused a problem but, when added together, meant a crash.

Ten employees of Metro and various consultants were slightly injured night while making test runs on the unopened section of tracks between Rhode Island avenue and Silver Spring.

The trains were both traveling south on parallel tracks and collided in a switch just north of the Rhode Island Avenue station. The switch, called an interlock, permits trains to cross from one track to the other and is used as the turnaround point for operations on the present Red Line.

What the operator of one train apparently did not know was that the switch had been changed. Furthermore, he did not receive instructions to "check your iron" or look at the switch before entering.

The result was that one train, which had the word, entered the switch and stopped to look. The other train, which did not have th word, rolled on through and rammed the side of the first train.

Such an accident would not happen in normal service, the report said, because automatic protections would be employed that had been overidden so the test trains could exceed normal speed limits.

When the automatic system is employed, as it always is during regular operations, the train brakes to a halt if it exceeds the speed limit for a section of track, regardless of what the operator wants it to do.

The lack of communication can be blamed on poor coordination between the regular train control room and the test control room and on faulty communication procedures between the front and rear cabs of one train, the report said.

Various administrative actions have been taken to tighten up the coordination between test and regular operations, the report said. The National Transportation Safety Board also is investigating the accident, but has issued no report.