on [XXX], we received the Tucson back from dealer from a complete engine replacement due to recall. On [XXX], our college son was returning to school from visiting a friend. He said he thought the car sounded a little different. There were no engine light warnings, so he didn't think much of it. About an hour into the trip, he started to smell gas, a few minutes later he started to smell smoke and saw smoke coming into the vehicle through the consoles. He looked behind him and saw a trail of fire and smoke. He decided to pull over but the brakes FAILED. He went into the median, applied the emergency brake and waited until the car slowed down. He was able to grab his phone that had fallen beneath his seat from driving onto the median. Once he was out of the vehicle, he could definitely see the car was on fire. It was entirely engulfed in flames within seconds. He called 911 and they were able to put out the fire within 30 minutes, but they commented that it was a difficult fire to extinguish. The car was completely destroyed front to back. We do not know if this problem started with engine, fuel tank or brakes. It is one thing when your car is on fire and you can pull over and get out. It is entirely another when you need to get out of your car but the brakes fail. You have to delay getting out of the car to ensure you don't hurt others on the road and save yourself before it explodes. We are lucky he is alive but are worried for others with this car.