The Ada Resource Association
Ada Used To Control Europe's Trains

Uniting the European Community

The goal of the European Community is to unite disparate countries into an interconnected, multi-cultural economic community. What began as a local project in Paris to improve the operation and safety of the railroads in France, has evolved into a Europe wide effort to provide a safe, smoothly run transportation system that will become a symbol of European community.

The Astree Project

This French project, called Astree, is an effort to equip every train with position and transmission systems that will automatically provide location, speed, distance, switch, operations, and safety information about each train. France's national railroad organization, Societe Nationale des Chemins de fer Francais (SNCF), in charge of the project, has chosen Ada and Rational for developing the systems that will collect, analyze, monitor, and control this data.

Astree's initial prototype consisted of 300,000 lines of C code, which was difficult to maintain and suffered reliability problems. Because Ada is recognized for its maintainability on large, complex development projects, Astree decided to start over using Ada. Astree's two main issues were safety and reliability of the software.

Approximately 15 software engineers will be working on the project, which is currently in the design phase. They are using the Rational Environment, Rational Compilation Integrator with DECAda, Testmate and Insight. The target system for the project is Digital Equipment Corp.'s VAX VMS and VAX/ELN using DECAda.

The early version of Astree, due to be completed by mid 1994, will control almost 100 trains over 600 kilometers of rail. By the turn of the century, it will be deployed over the entire territory, and even over Europe through the European Train Control System (ETCS) currently being developed in cooperation with Germany and other countries.

System Features and Equipment

Under the Astree project, each train will feature a train integrity control system and a computer that can control train speed and access data processing management and control centers across the territory through bi directional radio link. Each vehicle will also have an identification tag which can be read from the ground for consistent train information.

Other on board equipment will include Doppler radars that measure the current speed and distance covered. Each train will have a microwave reader that reads the track by collecting data from position transponders that are placed along the track. An odometric unit will input the data from the sensors and calculate the position of the train in the network.

All Astree operational centers are linked to each other and can query trains about their position and speed and determine the position of the switches. The centers rely on a computerized database that provides an accurate and comprehensive real time picture of the network and trains and supports monitoring, route setting, traffic control, and operational safety.

Apart from numerous technical developments in system components, the Astree project calls for integrated functional tests aimed at progressively developing operational specifications. At present, the main Astree functions are undergoing tests in the Paris suburbs, on the Bondy Aulnay line.

A comprehensive test of system function is also being defined and will include the greater part of the lines in the Eastern Parisian region. If this test confirms expectations, detailed functional studies could be completed by 1996 with actual implementation on the network before the turn of the century.

This article is based on an article written by Etienne Morel, Rational SARL.