Using Technology to Make Roads Safer: Adaptive Speed Limits for an Intelligent Transportation System

Adaptive speed limits (ASLs) is a promising technique that can be used to enhance the driving conditions on various road types. Consequently, a tremendous reduction in social costs can be achieved in areas such as accidents, pollution, congestion, noise, and greenhouse gas emissions. One of the essential factors in determining the efficiency of variable speed limit traffic systems is the dissemination of the adjusted speed limit. Several research studies indicate that in-vehicle driver notification significantly outperforms dynamic roadside speed limit signs. In this article, we present a framework outlining the system-level design and implementation for an ASL system with an interactive in-vehicle display and supporting communication units. We discuss three different realizations of the proposed approach, based on cellular networks, vehicular ad hoc networks (VANETs), and a hybrid cellular/VANET configuration. The hybrid system is designed and tested using standard components to demonstrate the feasibility of low-cost deployment.