Complex sentence: The Firmware 7.1 Autopilot update will include restrictions that will only allow the Autopilot system and its Autosteer feature to engage when the Model S is travelling below the posted speed limit.
Split into simpler sentences: The Firmware 7.1 Autopilot update will include restrictions on the system. The update will only allow the system and its Autosteer feature to engage when the Model S is traveling below the posted speed limit.