ramp travel index

Ramp travel index (RTI) measures how much a vehicle's suspension can compress and extend while the wheels stay in contact with the ground. It is expressed as a single number derived from driving the vehicle up a standardized ramp and recording the angle at which either the chassis or a fixed point on the frame first loses contact with the ramp surface. Higher RTI values indicate greater articulation and therefore better ability to maintain traction on broken terrain.

The measurement is performed on a device known as a ramp or tilting platform. The vehicle is driven forward onto an inclined plate, often set at a fixed slope angle, until the frame or undercarriage makes contact with the ramp surface while at least one wheel has lifted off. The angle of tilt at that moment, combined with measurements of the vehicle's wheelbase and the contact point, produces the RTI figure. This test reflects real-world performance on obstacles like rocks, logs, and washboard terrain where suspension movement determines whether the vehicle remains mobile.

RTI is particularly useful in evaluating purpose-built off-road vehicles, military vehicles, and rock-crawling platforms where ground clearance and suspension travel are design priorities. A vehicle with short wheelbase and long suspension travel relative to its height will achieve a higher RTI than a longer or stiffer vehicle of the same overall size. The metric is independent of horsepower or tire quality, focusing purely on the geometry and compliance of the suspension system.

Variants of the test exist; some use approach angle and departure angle as supplementary measurements, while others weight the RTI calculation differently depending on vehicle class. The usefulness of RTI is limited by the fact that it does not account for suspension stiffness, dampening, or roll characteristics, nor does it reflect performance at speed or on continuous rough terrain. A vehicle with high RTI but poor weight distribution or weak frame design may perform worse in practice than the number suggests.

RTI is most relevant to buyers and designers of vehicles intended for extreme terrain. For road-going vehicles or those with light-duty suspension, the metric is rarely cited. The term itself reflects engineering terminology rather than consumer marketing, making it a reliable benchmark within the off-road and military vehicle communities where suspension articulation is a primary design criterion.