This article describes the results of a feedback system designed to improve performance for a Swedish traffic police unit and examined whether such a feedback system was beneficial or detrimental to the attitudes of the officers. As in many Western countries, government organizations are being required to demonstrate their effectiveness with quantitative performance measures. An approach called the Productivity Measurement and Enhancement System (ProMES) was used with three groups of Swedish Traffic Police to do this. ProMES is a method for identifying unit's objectives, developing measures for these objectives, and using this information as feedback. ProMES was developed with these police units and feedback from the system was used over a four-year period. Results indicate that there were substantial increases in performance. There were also decreases in accidents, injuries, and fatalities compared both to baseline and to comparison groups in Sweden. These improvements were made with fewer and fewer police officers each year.