Following the rise of empiricism during the industrial revolution, the rational planning movement (1890–1960) emphasized the improvement of the built environment based on key spatial factors. Examples of these factors include: exposure to direct sunlight, movement of vehicular traffic, standardized housing units, and proximity to green-space.[5] To identify and design for these spatial factors, rational planning relied on a small group of highly specialized technicians, including architects, urban designers, and engineers. Other, less common, but nonetheless influential groups included governmental officials, private developers, and landscape architects.