Traffic Control Systems in Construction Work Zones

Traffic control devices in work zones are intended to provide sufficient guidance to motorists to help prevent collisions, especially with construction operations, and based on study of their use in Illinois, they appear to be meeting the objectives. What has been discovered in assessing work zone traffic control and crashes is that collisions occur more frequently than reports show and in ways not necessarily addressed in previous studies. For the most part, traffic control devices (TCD) within the actual construction area require no changes. They are protecting the workers from the motorists. What leads to collisions inside the work area are reduced lane widths and lack of adequate escape, especially on limited access roadways. As a result, the most frequent type of collision is rear-end, often caused by drivers stopping or suddenly slowing because of distractions. Outside the work area, the problem appears more related to poor driving behavior and need for some improved guidance for motorists, especially within the merge areas. When taking into account the under-reporting of crashes, with the exception of increases in certain manners of collision such as rear-end, the crashes appear no more severe than crashes occurring outside such zones. Crashes with pedestrians (which includes workers) also appear no more likely than in locations without work zones. On the other hand, crash reporting appears unlikely to include portions of the work zone away from the actual construction area. Using a set of crash reports in which the work zone was defined clearly to include the approach, taper, and exit, analysis suggests that crashes are almost as likely to occur outside the actual construction area as within. It is these crashes outside which appeared more severe and more amenable to enhanced traffic control, especially enforcement. The report recommends practices which could reduce crashes in the approach and where changes or reductions in lanes occur. In addition to other recommendations, a model for a process to be used in generating and reviewing work zone traffic controls has been developed.