DEFINITIONAny occurrence at an aerodrome involving the incorrect presence of an aircraft, vehicle or person on the protected area of a surface designated for the landing and takeoff of an aircraft. (Source: ICAO Doc 4444 - PANS-ATM). Note: the 'incorrect presence' may be a consequence of a failure of a pilot or vehicle driver to comply with a valid ATC clearance or their compliance with an inappropriate ATC clearance.MOST COMMON RUNWAY INCURSION TYPES- Incorrect entry of an aircraft or vehicle onto the runway protected area (without or contrary to ATC clearance or due to incorrect ATC clearance)- Incorrect presence of a vacating aircraft or vehicle onto the runway protected area- Incorrect runway crossing by an aircraft or vehicle (without or contrary to ATC clearance or due to incorrect ATC clearance)- Incorrect spacing between successive arriving or arriving and departing or departing and arriving aircraft- Landing without ATC Clearance- Take-off without ATC ClearanceCONSEQUENCESThe biggest risk of a runway incursion is that at least one of the aircraft involved will be travelling at high speeds which increases the chances of substantial damages or even fatal injuries.CONTRIBUTING FACTORS- Weather. Low visibility may increase the chance of flight crew becoming disorientated - Aerodrome design. If aircraft have to cross active runways to move between their take off or landing runway and their parking position, the chances of runway incursions is increased. - Conditional Clearances If conditional clearances are used, the risk of any error may be increased..- Phraseology Use of Non-Standard Phraseology can lead to clearance confusion and misunderstanding between flight crew and controllers. - Use of More than One Language for ATC communications. At some international airports, locally-based users are permitted to communicate in the local language while foreign aircraft do so in English. - Excessive Workload.