Multimodal Accessibility of Modern Roundabouts

Abstract

Modern roundabouts have become popular in North America during the past decade. This popularity can be attributed to their great success in Europe and Australia. There has been significant debate, however, over their accessibility for pedestrians. With almost uninterrupted traffic flows, roundabouts make it difficult for the visually impaired to determine safe gaps, as they rely on auditory cues alone. Such crossing is particularly complicated by ambient noises and circulating vehicles on busy urban roundabouts. Various pedestrian signals have been installed at roundabouts overseas. The United States Access Board published a draft guideline proposing pedestrian signals at all roundabout crossings to ensure access for the visually impaired. Roundabout operations can be a complex process of transporting multimodal travelers. There is increased interest in harnessing artificial intelligence to address issues to improve transportation systems. This research developed a crosswalk signal and introduced fuzzy logic control (FLC) into the signal timing to accommodate roundabout users. The system was assessed against the Pedestrian User-Friendly Intelligent (PUFFIN) crossings under varied geometries under different traffic conditions. The objective was to identify potential treatments for improving roundabout accessibility, safety, and efficiency. The results reveal that “distant” layout reduces vehicle delays and queue lengths when the FLC signal is applied, especially under saturated traffic conditions. From safety and operational perspectives, the FLC signal outperforms PUFFIN. The FLC signal implements the signal timing effectively, decreases pedestrian delay, and maintains adequate vehicle circulation. Multimodal traveler needs at a modern roundabout are satisfied in manifold ways.