Speeding behaviour and driver distraction cause relative unsafety at highway work zones and amongst young male drivers. Adding further safety measures to the infrastructure has adverse effects as drivers may compensate for improved safety by driving faster. This study investigates whether in-car warnings on a head-up display (HUD) improve speed compliance and speed behaviour of young male passenger car drivers at work zones. A HUD warning system was tested in a repeated measures fixed-base driving simulator experiment with 34 participants. Drivers slowed down sooner and smoother when the warning system was enabled, but speed behaviour at the work zone was not different when the system was active. Drivers who sped outside of the work zones had lower pre-experimental satisfaction of the system although this increased to normal levels during the experiment. Perceived effects of the system were limited to a small reduction in stated mental effort. This is in line with literature findings. Although the system improves speed behaviour in the slow-down area and may have a positive effect on traffic safety, it does not improve speed compliance at work zones. The system can reach its target audience by integrating it with systems which provide directly perceivable benefits to drivers. Further research is required on the effects on other driver groups and the potential of personalised situation-aware warnings.