Nonholonomic constraints depend on the particle velocities, accelerations, or higher derivatives of position. The data measured within WIAMan includes forces, movements, accelerations and angular velocity. This may, therefore, explain decreased coordination at higher movement velocities and accelerations. Linear accelerometers measure non-gravitational accelerations of the vehicle. In non-inertial coordinate frames, other "inertial accelerations" associated with rotating coordinates may arise. Somatogyral illusions occur as a result of angular accelerations stimulating the semicircular canals. Parts of this diagram represent distances, other parts gravitational accelerations (attractive forces per unit mass). Tests involved lateral and vertical accelerations and pitch and roll. During elite racing the rider experiences accelerations up to 5g and reaches speeds over . Sudden accelerations in the lateral plane result in a rough ride. The saccule detects linear accelerations and head tilts in the vertical plane. Somatogravic illusions are caused by linear accelerations. The utricle detects linear accelerations and head-tilts in the horizontal plane. This allows for very high speed and high accelerations. ACN systems are activated by detecting crash-strength accelerations.