One South Dakota study has shown that the presence of the highway patrol can reduce traffic speeds in work zones, but unless officers actually issue citations, the effect of presence alone is temporary. Sufficient numbers of officers are not available for continuous enforcement. Furthermore, intensive enforcement activities within the work zone could aggravate congestion and traffic conflicts within the work zone.
Other jurisdictions have found that the use of automated speed enforcement devices can provide similar speed reductions and substantially raise drivers' awareness of speed limits. Automated speed enforcement systems consist of a narrow-beam radar speed detection unit and one or more flash cameras that photograph vehicles exceeding a specified speed threshold. After violations are detected, the film is processed to reveal speeding vehicles' license numbers and their recorded speeds. The owner of the vehicle is mailed a citation and assessed a civil penalty, in much the same manner as a parking violation might be handled. Because the vehicle owner , not necessarily the driver , is cited, the violation is not a normal speeding violation, and the owner is not assessed points against his driving record. Similar systems have also been used to reduce red light violations.
The speed enforcement system to be evaluated in this study differs from photo radar systems in both the camera and the speed detection method used. Rather than using a still camera together with a traditional radar gun, the LaVideo system uses a video camera with a Lidar unit - a very narrow beam laser unit that is capable of detecting a small target speeding within a group of larger vehicles. The LaVideo system also differs from photo radar units in that it must be manned to keep the camera and Lidar trained on the vehicle.
Initial work was done during the summer of 1997 to evaluate two of the laser video units. These units were operated by a SDDOT employee along with a Highway Patrol officer. Violators videotaped while speeding through workzones received warning letters, not citations. Only five warnings were issued.
Although automated speed enforcement systems have been well demonstrated in fixed speed zones, they have not been widely used in work zones. Demonstrating their ability to reduce vehicle speeds in work zones will be a worthwhile endeavor, not only for South Dakota, but also for the rest of the nation.