After a pair of workers? deaths, the agency that runs New York's subway system tested a sensor to alert crews of oncoming trains.

The system was tested Friday and it gives track workers a sensor, which is linked wirelessly to other detectors mounted on trains. When a train approaches, workers hear a ring or vibrating alarm. The units could also be set to trigger flashing lights.

The new system comes in the wake of two incidents in April where track workers were struck and killed by oncoming trains.

An MTA spokesperson says the agency will evaluate the results of Friday?s test. He added, the sensor system performed well.

Maintenance workers were also retrained on track safety.