Lateral Vision Angles in Roadway Geometric Design

Abstract

One of the main safety factors in merging areas and at skewed intersections is lateral visibility. Two field studies have been conducted to investigate both the vision angles from rear-view mirrors and the dimensions of the best-selling cars in Spain. The impact of the available lateral visibility in merging areas and at skewed intersections has been evaluated, and safe skew angles at both locations have been proposed. A minimum direct field of vision of 220° for drivers was assumed, while design vehicle dimensions were determined from measurements. Then, a skewed intersection that offerred an adequate intersection sight distance was determined. Taking into account the experimental lateral visibility design angles and the dimensions of the design vehicle, a new design has been proposed for merges during which no vehicle can be found in the driver’s blind spot. Another model was proposed for safe lane changing. Minimum angles of vision for the left and right rear-view mirrors in lane changing were determined to avoid the presence of vehicles in the driver’ blind spot.