Ramp travel index or RTI, is a way of measuring a vehicle's ability to flex its suspension, a property also known as axle articulation. The RTI rating is used mainly in the off-roading industry to test and describe chassis limits of modified vehicles.
The ramps vary between 15 and 30 degrees of angle for the vehicle to ride up. "Ramping" a vehicle involves putting one front tire on the ramp and driving up slowly until one of the other three tires (usually the rear one on the same side as the tire driving the ramp) begins to leave the ground. The measurement is only taken when the other three tires are still on the ground. The distance traveled up the ramp is then measured and is divided by the vehicle's wheelbase and finally multiplied by 1000 to give a final RTI score.[1] Most stock SUVs have RTI values from 400 to 550;[1] vehicles modified for off-road competition have the ability to exceed 1000.[2]