Roundabouts in the United States: An International Comparison of Illuminance Requirements and Costs

Abstract

United States federal guidelines recommend systematic illumination of roundabouts in both rural and urban areas. However, competing conventional intersections in rural areas can be kept unlit. Highway illumination is also a major contributor to intersection operating and maintenance costs. This paper reviews roundabout illumination policies from 44 countries to determine if systematic illumination is normal practice and if not, to identify the warranting conditions. In addition, this paper compares the illumination level requirements and implied costs for three reference U.S. rural roundabouts with their equivalents from 15 selected countries. Professional lighting design software, DIALux®, was used to build roundabout illumination models corresponding to the recommended illuminances in the study countries and the simulation outputs were converted into annual operating costs to facilitate the comparisons. The findings indicate that most countries (approximately 59%) do not require systematic illumination of roundabouts in rural areas. While a few countries (approximately 16%) do attempt to illuminate all roundabouts it is more common to find such a requirement in urban areas. The study also finds that the average minimum maintained illuminance is higher in the U.S.A. than in Europe and the United Kingdom. However, the U.S. tax payer pays significantly less than their counterparts in the other countries studied. These findings are significant because the desired proliferation of roundabouts in the U.S.A. would receive a significant boost if the U.S.A. were to adopt lower illuminance levels, a non-systematic illumination policy, or both, for rural roundabouts.