Ejection seats were necessary measures in 2015 with the advent of hover conversion. As vehicles might collide in mid-air while traveling along the skyways, another method of escape was devised, in this case the ejection seat, which may have allowed the driver and/or passenger(s) to eject upon impact. On the 2015 Hill Valley greeting sign, flyers were reminded about the importance of ejection seats ("PLEASE FLY SAFELY / EJECTION SEATS SAVE LIVES").