Not really urban -- feel free to alter the scenario to answer the question you prefer, but...

You're driving along a lightly traveled back country road miles from nowhere and happen upon a head-on, one driver is already gone but the second unlike the first was strapped in and is still alive but in bad shape. You have a FAK in your trunk, and while calling 9-1-1 (you do have cell coverage) you get the FAK and prepare to assist the surviving driver.

You can define bad shape as you choose (considering the scope of injuries that could be sustained in the head-on collision), but besides a complete trauma center, what would realistically be in a good FAK designed for such a scenario? Realistically, how many 4x4's and 5x9's? Quick Clot? What else?

If you like pick a commercially available kit and mark it up to make it better.