Previous research has found that commercial drivers get an average of 5.18 h of sleep per night. The revised hours-of-service (HOS) regulations (in the United States) are in place to provide drivers with more opportunities to get sleep. However, are drivers really getting more sleep under these new regulations? Also, is there a relationship between sleep quantity and involvement in critical incident (crashes, near-crashes, or crash-relevant conflicts)? Data from 73 truck drivers, collected during a naturalistic driving study after the implementation of the 2003 HOS regulations, were analyzed to determine overall sleep quantity (using actigraphy), along with sleep quantity prior to being involved in a critical incident. Sixty-two drivers had at least seven consecutive days (Monday through Sunday) of reliable actigraphy data; mean sleep quantity per 24-h period (midnight centered using the Cole-Kripke algorithm) for these drivers was 6.28 h (S.D.=1.42 h). Fifty-eight critical incidents were recorded in the 10th and 11th driving hours. Analysis results indicated that drivers received significantly less sleep in the period prior to a critical incident as compared to their mean overall sleep quantity. The results of this study indicate drivers may be getting more sleep under the revised 2003 HOS regulations as compared to the old regulations. In addition, significantly less sleep in the 24-h period prior to involvement in a critical incident suggests driver fatigue may have been a potential contributing factor in these critical incidents.