Abstract: One variation of a method includes, during a first time period: detecting a direction of motion of a trailer; detecting a first force applied to a kingpin; detecting an incline angle of the trailer; calculating a first target preload force opposite the direction of motion and inversely proportional to the incline angle; and in response to the first force falling below the first target preload force, triggering a motor to increase torque output opposite the direction of motion. The method further includes, during a second time period: detecting a second force applied to the kingpin; detecting a decline angle of the trailer; calculating a second target preload force opposite the direction of motion and inversely proportional to the decline angle; and in response to the second force falling below the second target preload force, triggering the motor to increase torque output opposite the direction of motion.