Intersection Modifications Using Modular Mini Roundabout Methods

Date: 12/08/2021

Conversion of traditional intersections (stop controlled and signalized) to modern RABs has been a growing practice in many countries around the world including the U.S. – largely due to the benefits of reduction in crash frequency and severity, capacity improvement, and operational improvement. However, construction of traditional RABs is costly and requires additional right‐of‐way (ROW) which can deter roundabout installation on local transportation systems that have budgetary and/or available ROW restrictions. The main objective of this project was to develop guidelines for ORIL on the installation and performance of mini‐/modular‐RABs considering characteristics of Ohio’s local transportation system. Based on published guidelines and from existing pilot implementations (both international and within U.S.), current design practices considering traffic condition and roadway conditions were identified. Based on survey findings, there was a reasonably high level of familiarity with mini-RABs among respondents. Most agencies consider reduction of crashes/severity and improved traffic operations in installation of mini-RABs. Major concern with mini-RABs is drivers neglecting the central island and driving straight through thus causing the mini-/modular-RAB to lose its integrity. Agencies typically place mini-/modular-RABs on two-lane highways with low traffic volumes (15,000 vpd); and/or peak-hour volumes of 1,600 to 1,800 vehicles. Based on driving simulator experiments, there are no differences in critical gap as driver’s maneuvered through mini-RAB of different ICDs. Operations-wise, Mini-RABs with larger ICDs performed better than those with smaller ICDs.