Adaptive treadmills (ATMs) that change speed based on the users\' gait mechanics can allow for healthy stride to stride variability observed during overground walking, while maintaining the benefits of traditional treadmill training for gait rehabilitation. To enable unilateral targeting of propulsion, we developed an adaptive split-belt treadmill (sATM) that updates the speed of each belt of the treadmill based on the user\'s propulsion and position. The present study validated the sATM against an existing tied-belt ATM that updates the speed of both belts based on the user\'s propulsion, step length, and position. We also determined the effect of modifying the importance of propulsion unilaterally on the sATM. To validate the sATM, fourteen young, healthy participants completed five trials at their comfortable walking speed on the tied ATM and sATM with unilateral and bilateral modifications. We hypothesized that propulsion and walking speed on the novel sATM would be equivalent to the tied ATM, and further that the sATM could be preferentially weighted to encourage higher propulsion unilaterally while maintaining walking speed. Participants maintained similar propulsion and walking speed between treadmills and belts for bilateral modifications. While a few participants increased unilateral propulsion to maintain similar walking speeds for the unilateral modification, others showed no change in propulsion with slight differences in walking speed. Our results suggest that the response to unilateral modifications was user-specific, and the sATM could be tuned individually to allow unilateral control strategies. The present study demonstrates that walking speed can be modulated on an adaptive split-belt treadmill.