ST. CLOUD (AP) - New safety technology that may have prevented the deadly train crash in New Jersey is being implemented along some rail lines in Minnesota and elsewhere, but is years away from completion.

The new safety technology, known as positive train control, is designed to automatically slow or stop a train to prevent accidents such as a collision with another train or a derailment caused by excessive speed.

In 2008, Congress passed the Rail Safety Improvement Act, which required positive train control technology to be implemented on all Class I passenger lines and freight trains carrying certain hazardous materials by 2015.

Congress delayed that deadline last year for at least three years after railroads said installing such a complex technology has never been attempted on such a large scale.