Vehicle accident analysis relies heavily on mathematics and the principles of conservation of energy and momentum and Newton's laws of motion. In order to apply these principles, it is first necessary to know the approximate vehicle motions. The analytical procedure is interactive using a combination of model analysis and computer-aided engineering analysis to determine linear and angular velocities and accelerations. Scale accident scene models combined with aerial photography to enhance realism has been extensively utilized in evaluation, analysis and presentation of vehicular accident reconstructions to non-technical audiences. Slide and video accident animations have been produced directly from aerial photograph enhanced models and have been used successfully in courtroom presentations since the 1970's.