Development of a model for determining workzone illumination requirements during nighttime highway construction

With the increasingly popularity of nightwork on many highway construction projects, a number of complex problems have been introduced in highway rehabilitation. Of many issues involved, workzone lighting is found to be the single most important factor affecting quality, safety, cost and productivity on these night projects. At present, lighting requirements in the workzones are minimally defined in the specifications of few state highway agencies and often times are not formally designed as there is no standard or guidelines to go by. Although a number of research studies have been performed in roadway lighting and industrial lighting area, no formal study determining illumination requirements in the workzones has been conducted. In this research effort an attempt has been made to identify the typical highway construction tasks performed at night and the factors affecting illumination requirement to adequately conduct these operations, and to develop a model determining average maintained light intensity levels for the tasks. In an effort to provide an overview of nighttime highway construction and provisions for lighting, an extensive literature review was conducted. As a result of nationwide questionnaire survey, various highway operations commonly performed at night were identified. Significant factors influencing illumination requirements for workzone lighting were also identified. These factors included: (a) speed, (b) accuracy or importance, (c) reflectance, (d) seeing distance, and (e) size of object. These factors were assigned certain subjective levels for comparing with visually similar outdoor industrial tasks. Various illuminance level categories were determined based on IES and OSHA recommendations, state provisions, opinions of experts and experiences during field reviews. The categories were intended to be interpreted as recommended safety requirements and not regulatory minimum requirements. A model approach was adopted to determine illumination levels for any given construction task. Correlation analysis was performed to examine the association of various factors with illumination requirement. Trial models were suggested and analyzed using SAS procedures. The most appropriate model was selected and validated using three real life case studies. For all the case studies which represented most commonly performed highway construction tasks at night, the results conformed to the field recorded values. From the opinions of the crew at the job-site and experiences while recording the observations, it was concluded that the results from the model were in agreement with the findings.