The Federal Aviation Administration lists the reduction of runway incursions among its top priorities. The FAA defines a runway incursion as an "unauthorized presence on a runway, regardless of whether or not an aircraft, vehicle or pedestrian presents a potential conflict to an aircraft authorized to land, take off, or taxi on a runway." Runway incursions range from two planes colliding while taxiing, taking off or landing, to lesser incidents where a vehicle, person or object is in an area where it should not be but is removed before any safety consequences arise.
A runway incursion occurred yesterday at Newark airport when a plane operated by Scandinavian airline SAS collided with another plane while taxiing. The SAS plane lost part of a wing in the incident. The other plane, a United Airlines ExpressJet Embraer 145 lost its tail fin and had to be towed back to the terminal. Thankfully, none of the 253 passengers on board the SAS plane or any of the 31 passengers on the United Airlines plane were injured.
It is not yet clear what caused the two planes to collide. It appears the planes were lined up to take off when the SAS plane turned to get to a different taxiway and clipped the United plane in front of it.
In 2011, the National Transportation Safety Board listed runway safety on its Top Ten Most Wanted List of safety initiatives. The group listed improving the situational awareness of pilots and increasing the time they are given in which to take action to avoid collisions as the keys to reducing the likelihood of runway collisions.
The Newark collision is currently under investigation by safety authorities.
Source: The Local, "SAS plane loses part of wing in Newark collision," 2 May 2013