When people think of airplane crashes, they generally imagine a sudden technical malfunction in mid-air, ending with a plummet to the ground. In reality, much of the threat to airplane passengers occurs on the runway itself, before or after the actual flight. For example, in August 2006, 49 people died when a commercial plane crashed into a fence and burst into flames in a field in Lexington, Kentucky [1]. At Los Angeles International Airport in October 2006, two jets on the runway came within 100 feet of colliding with each other [2]. In October 2001, at the Linate Airport in Milan, Italy, two planes crashed into each other, killing 118 people and leaving no survivors [3].

The above incidents are all examples of runway incursions. The Federal Aviation Administration (FAA) defines a runway incursion as an incident where an aircraft (which is taking off or landing) and another aircraft, person, or vehicle on the ground either collide or come dangerously close [4].

Runway incursions have repeatedly topped the National Transportation Safety Board's list of "Most Wanted" safety improvements for the past decade [5]. These incursions happen frequently and at every airport, creating a major risk for pilots, airport employees, and passengers worldwide. Runway incursions are a serious concern at today's airports because they can potentially lead to major disasters. In order to decrease the risk of collisions and increase passenger safety, the number of incursions must be significantly reduced.

A large number of factors contribute to runway incursions. Planes and jets are designed to be agile in the air, but they are clumsy and extremely difficult to maneuver on the ground. As aircraft are very large and rather bulky, there is little room for error during the processes of taking off and landing. The cramped and complex configurations of runways and taxi routes at airports make taking off and landing even more difficult. Pilots and ground drivers must ensure that their vehicles are in the right place at the right time while tower controllers coordinate the movements of multiple planes simultaneously (Fig. 1). These human capabilities are often affected by the weather, aviation rules and demands, and stress. Incursions are a particularly difficult problem to solve because of these numerous contributing issues.

The workload and stress on controllers and pilots can greatly affect their ability to consistently make correct decisions on the runway. In the air traffic control tower, controllers must "orchestrate the mix of arriving, departing, and taxiing aircraft as efficiently as possible, in order to avoid aircraft delays and maximize the capacity of the airport" [6]. Controllers continuously analyze raw data from the radar reports, decide on the best paths for different aircraft to take, and relay instructions to pilots in every plane. This becomes increasingly difficult when weather blurs visibility, construction changes the utility of certain pathways, and an airport takes on larger loads of traffic.