The Metropolitan Transit Authority began testing Positive Train Control on two of its major lines this week.
Positive Train Control is a technology designed to reduce the potential for human error by automatically slowing trains under certain circumstances.
The tests are running on the Montauk Branch of the Long Island Rail Road during off-peak hours until this Friday, and will start back up again the week of October 29.
Customers can expect up to 88 minutes of additional travel time.
Metro-North service will also be affected this week as crews install Positive Train Control technology on the Upper Harlem Line.