The Federal Motor Carrier Safety Administration and the National Highway Safety Administration, as well as other local, state, and national organizations regularly conduct enforcement programs geared toward improving safety on the nations roadways. Many of these programs are very successful; however, others indicate far less success. Previous research shows that a lack of success in these programs, in large part, may be due to the fact that the enforcement waves conducted under many of these programs may not be as well understood. Successful programs like Booze-It-and-Lose-It and Click-It-or-Ticket clearly convey what is being enforced when citizens drive through checkpoints; however, other programs are less likely to convey to drivers what is being enforced. Instead, citizens tend to believe speeding is the primary intent of patrols during an enforcement wave. This research studies the effect of portable changeable message signs PCMS on aggressive driving behavior through a 6-mile enforcement zone. The PCMS is installed at the site over a four-month period, while enforcement is only conducted during a short one-week wave. Traffic was monitored at two interchanges just downstream of the sign, one and six miles away. The sign alone was not found to significantly affect traffic behavior through the 6-mile zone; however, supplementing the signage with enforcement did show positive effects, in addition some long-term impacts one month after enforcement for some measures. PCMS was shown to be a viable tool for enforcement agencies to convey the meaning of the enforcement waves. In addition, these findings indicate a positive correlation in the sustained effect after enforcement leaves the site.