Prototype design and experimental evaluation of wireless measurement nodes for road safety

Highlights

• An innovative infrastructure called Wireless Active Guardrail System (WAGS) is presented.

• We propose measurement nodes for increasing traffic safety.

• The prototypes design for speed and proximity measurement nodes are shown.

• We present the measurement characterization of prototypes of measurement nodes.

• Their experimental evaluation are reported and discussed.

Abstract

The paper presents the design and the experimental evaluation of prototypes of measurement nodes that are part of the Wireless Active Guardrail System (WAGS). The WAGS is an innovative infrastructure, allowing increasing traffic safety on roads, by monitoring vehicle speed, proximity between vehicle and guardrail, impact of a vehicle with the guardrail, and several environmental parameters. In particular, in this paper, the designs and prototypes of the nodes dealing with speed and proximity measurements are presented. Then, all the phases of their experimental evaluation are reported and discussed.

Introduction

Although safe road traffic is a goal of governments and civil society all over the world [1], nearly 3400 people die on the world’s roads every day [2]. Tens of millions of people are injured or disabled every year [2]. The speed of vehicles represents one of the basic risk factors in traffic safety, and therefore, the accidents (e.g. vehicle crashes, vehicle impacts with guardrails) depend by several factors [3]. For example, it is known that if the driven speed gets higher, the crash rate increases, and to this aim, a variety of countermeasures (e.g. by using remote and distributed measurement/actuating systems) should be taken into account.

In order to face this challenge, one of the main objectives is to improve the road infrastructure, such that it can have a protective role in preventing accidents. With the growth of technological development of the embedded systems, since past two decades, it was possible to implement and deploy the concept of Intelligent Transportation System (ITS) [3]. Due to the minimization of size and low power consumption of modern sensor technologies, it was possible to create new sensing systems which can be mounted among the roads in order to monitor them. Nowadays, different types of measurement systems, such as for: vehicle speed, traffic jam and air pollution, are available on roads as part of ITS. They are mounted by using additional mechanical structure elements or directly in road pavement, and an important observation, they are far spread from each other (e.g. as range, between hundreds of meters or kilometers) [3].

In this framework, a novel idea, consisting of a Wireless Sensor/Actuator Networks (WSANs or simply WSNs) for traffic safety has been proposed in the project called “Design and prototyping of a new barrier based on an innovative concept of safety combining structural function (passive function) and active function” [4]. The idea consists of designing an active infrastructure, embedded on the road guardrails, which is capable of monitoring the traffic on the road, the road conditions, and to take some actions directed to the prevention of collisions between vehicles and guardrails, and to promptly alert an emergency system when an accident has happened.

This active infrastructure, called Wireless Active Guardrail System (WAGS), has been presented in [5], [6]. In [6], [7], [8], [9], two node architectures for traffic safety measurements and their roles have been described. Such nodes have been designed to measure: (i) the vehicle speed, (ii) the proximity between vehicle and guardrail, and (iii) the acceleration of the guardrail parts, subjected to an impact with a vehicle. In [7] a mathematical model for the measurement uncertainty, for each traffic safety measurement, has been presented. Finally, in [8], a preliminary work about laboratory characterizations of the developed speed and proximity measurement systems has been reported.

This paper aims of presenting and discussing the prototype design and the experimental evaluation of the developed speed and the proximity measurement systems. Laboratory tests and on field tests have been carried out, in order to assess the accuracy of the designed measurement systems and their actual applicability on the road infrastructure. The obtained results show that the proposed speed and proximity measurement systems can be suitable for a practical use, inside the WAGS.

After the introductory section, the paper is organized as it follows. In Section 2, an overall overview of the WAGS architecture is given. Then, in Section 3, the prototype design of the speed and proximity measurement systems is reported and discussed. The metrological characterization of the speed and proximity measurement system is presented in Section 4. The laboratory and on-field experimental investigation phases are described in Section 5. Finally, in the last Section, several conclusions are drawn.