Describe buildings, nearby aircraft, signs, directions, painted lines or terrain. A small percentage of these ground accidents occur due to runway incursions. An aircraft goes on to a runway where it does not belong. However, several hundred incursions occur every year that do not result in accidents. A clearance to taxi to a runway allows you to cross all runways and taxiways on the way but does not allow you to go on the assigned runway or any parallels at any point.
Memory loss is the number one cause of controller errors.
Distraction is the major cause of this loss of memory. Controllers may make a separation misjudgment by mistakenly making speed assumptions that are not there. Controller coordination or phraseology in the tower between local and ground can be a problem if an aircraft is cleared to taxi in front of a landing aircraft. The last area of causes is communication, which comprises a vast range of problems. Readback and hearback is a forever difficulty.