Aim The study investigated how a speed warning system influence drivers’ speedometer monitoring, and how drivers respond when they receive a speed warning. With a speed warning system, drivers may pay more attention to the exact speed, which would be expected to increase glances to the speedometer. Methods Nineteen participants drove in a driving simulator, either with or without a speed warning system implemented on a smartphone, which alerted them if they exceeded the set speed limit. Their glances to the speedometer and speed warning system’s display were recorded with an eye tracker. Results Drivers sped less with the warning system. The system did not significantly change the speedometer monitoring. Speeding was preceded by fewer speedometer glances, indicating the speeding was linked to participants’ momentary inattention to their speed control. After a warning, the frequency of speedometer glances increased. Interestingly, drivers often started to glance at the speedometer and release the accelerator a couple of seconds before a warning, suggesting that drivers learn to anticipate warnings. The results suggest that drivers do not only react to warnings, but they also actively try to avoid them. Understanding drivers’ speed control with speed warning system may help to create adaptive ISA systems.