There are several factors that are relevant and significant.
Suppose x-sector was in a vaccum and the track had zero friction and was at 90 degrees then most would agree that both object would fall at the same rate and land at the ground at the same time. Then most people would be wrong. The inertia (resistance to change in velocity due to an acting force) of the oblivion car at zero velocity is much higher than a person due to inertia being dependant on mass.
Lets now allow the people riding oblivion to breathe and add air into x-sector but keep the track at 90 degree with zero friction. What we need to do know is work out the terminal velocity of the car and of a person. Fortunately there is a handy website http://www.grc.nasa.gov/WWW/k-12/airplane/termv.html
that helps with the calculation. I used 4 tonnes for the oblivion car, a cross sectional area of 10sqm (imagine front on view so a rough guess), a drag coefficient of 1.28 (flat plat perpendicular to plane of travel) and an altitude of 100m asl. This gives a terminal velocity of the oblivion car of approx 158mph. Obviously it never reaches this but this is my theoretical maximum for a much larger version of oblivon.
The terminal velocity of a person is approx 120mph (common knowledge). As a falling body drops through air the drag increases untill the upward pressure equals the acceleration due to gravity and terminal velocity is reached. If an object has a higher terminal velocity than another, then therefore the rate of drag increrase must be slower as the acceleration due to gravity is constant. to illustrate with made up numbers, suppose the drag of the oblivion car increased by 0.1 metres per second per second then the net acceeration would look like this in 1 second increments :- 9.8, 9.7, 9.6, 9.5, 9.4 etc etc.
Suppse for a person the drag increased by 0.2 metres per second per second then the net acceleration would become 9.8, 9.6, 9.4, 9.2 etc etc
As you can see the oblivion car has a higher net acceleration than the person on their own as it has a higher terminal velocity.
As is well known the track is at 88.8 degrees not at 90. this is to stop the car wheels leavnig the track making for a smooth ride as they dont hit the track again, and causes less wear and tear. So this tells us that the oblivion car is never in free fall. But why 88.8, why not 89.2 or 87.6. One could argue that this is the maximum angle to allow the car to be at almost but not quite free fall. due to the calculations for the friction and angle of attack being pretty complex I am going to assume that 88.8 degrees is the perfect angle with minimal slowing on the car (yes this is incorrect).
So my conclusion is that the oblivion car will fall faster than a person without the car due to it having a higher terminal velocoty. The overall efefct will be small though due to the drop length being relatively small.