pass along
軼 centers on moving past or surpassing: passing along, overtaking, or going beyond a limit. The given meaning 'pass along' fits this idea of moving past a point.
軼 combines 車 (vehicle) with 失, which likely contributes the sound and the idea of losing or escaping, together suggesting a vehicle passing by or overtaking.
A vehicle (車) that loses (失) its place in line speeds past the others: 軼 means passing along or overtaking.
For イツ, imagine a vehicle that eats up the road as it passes: eats -> イツ, and the car zooms past.