From the Roosevelt Island Twitterverse:

The Roosevelt Island Operating Corp ( RIOC ) issued the following advisory explaining what is happeing:

Please be advised the New York City Fire Department (FDNY) will be conducting a training session on one Tram cabin on Wednesday, May 1st, from 10 AM to 2 PM.

As part of the training exercise, FDNY personnel may be climbing on top of or rappelling from a suspended Tram cabin.

Tram service will not be disrupted.

Sincerely,

Roosevelt Island Operating Corp Advisories Group

More on Roosevelt Island Tram Rescue Drill, including video from previous posts.