TUTORIALS

Case studies

This chapter presents you with case-studies that will take you through the complete design process – starting from the purpose of the service up to the logical architecture of the service. Since SafeTRIP is an open platform, its design supports and facilitates the development of ITS services. You therefore do not require a very deep understanding of satellite or communication technologies to develop for SafeTRIP.

Three case studies are presented and each highlights a particular category of typical usage scenario for an ITS platform such as SafeTRIP.

-      Case study 1 – Management of traffic flows

-      Case study 2 – Traffic monitoring

-      Case study 3 – Emergency call

In order to fully comprehend the case studies, you would have read the previous sections of the tutorials. By the end of this chapter, you will be able to design services that will exploit the SafeTRIP platform.

Case study 1 – Management of traffic flows

Background

Traffic flow management is a typical hot topic for ITS researchers. Many theories and models exist for predicting and describing traffic congestion, as well as algorithms for redirecting the vehicles to alternative roads and solving the jams. Although theoretical solutions are available, applying them is not straightforward, due to the difficulties to access the dozens or hundreds (sometimes even thousands) of concerned cars affected by large-scale congestions, in a timely and cost-effective manner.

As a vehicular communication platform, SafeTRIP provides a powerful tool to centralize and implement solutions to traffic congestion: information on the traffic status is handled in a centralized way at server level, and instructions on how to react are transmitted to all the involved vehicles.

What is the service about?

This case study describes how to design a basic application for traffic re-routing based on SafeTRIP.

Use case

A typical use case would be as follows. The road operator detects a congested situation on one of its carriageways. Several alternative paths are then computed, at the service centre, to allow the drivers to bypass the affected area according to their entrance and exit point of the congestion, and actualized according to the real traffic condition. These paths, in the number of N, are then communicated to all the cars in the region (equipped with the SafeTRIP OBU). The vehicles interested in crossing (or leaving) the congested area then use the received suggestions to re-calculate their itinerary; random functions can be introduced on the OBU to select among several suggested alternative paths, to reduce side effects.

The difference with a traditional GPS navigation system is that the alternative paths are computed in real time and keeping into account dynamic factors related to traffic flows, road works, accidents, etc.

A first version of the application makes use of the following enabling services provided by the platform:

-     Positioning service – required by the OBU to know its position, determine whether it is affected by the rerouting alerts and compute the best alternative itinerary;

-     Datacast service – used to transfer the alternative routes.

At a lower level, the application makes use of one of the communications services offered by the SafeTRIP platform: broadcasting services.

The developer starts by defining the overall logical architecture of the system (see figure below).