The effects of human-machine interface (HMI) design for intelligent speed adaptation (ISA) on driving behavior and acceptance were measured in a moving-base research driving simulator. Sixty-four experienced drivers participated in two simulator experiments (32 in each). During the simulated runs with ISA, the speed limit was communicated through the ISA system. The ISA system consisted of an indication of the speed limit on the speedometer and a gas pedal that could be used either as a haptic or tactile pedal or as a dead throttle. Two versions of the haptic gas pedal were examined in Experiment I: a low-force ISA (easy to overrule, informative in nature) and a high-force ISA (stronger counterforce, more compulsory in nature). Two other configurations were tested in Experiment II: a tactile pedal (a vibration on the gas pedal, informative in nature) and a dead throttle (completely restraining the driver from exceeding the speed limit). It was hypothesized that the closer the ISA is to an informative type, the higher the acceptance and the smaller the effects on driving behavior would be. This hypothesis appeared to be valid, although for both driving behavior and acceptance, not all four HMIs could be ranked unambiguously on the scale from no ISA to full ISA. In sharp curves, drivers appeared to choose a driving speed below the speed limit, irrespective of ISA. The specific road environment scenarios that were inserted to examine presupposed compensatory behavior for experienced delay indicated no signs of compensatory driving behavior.