SACEM (railway system)
| Company type | Technology system |
|---|---|
| Industry | Railway signalling |
| Founded | 1980s in France |
| Founder | GEC-Alsthom, Matra (now Siemens Mobility), CSEE (now Hitachi Rail STS) |
| Headquarters | France |
Area served | Rapid transit railway systems worldwide |
| Products | Automatic speed control and train operation system |
The Système d'aide à la conduite, à l'exploitation et à la maintenance (SACEM) represents an integrated, automatic speed control mechanism tailored for rapid transit railway systems. Its designation translates to "Driver Assistance, Operation, and Maintenance System."
Originating in France during the 1980s, SACEM was developed through a collaboration between GEC-Alsthom, Matra (currently Siemens Mobility), and CSEE (now Hitachi Rail STS). The system's inaugural implementation occurred on Paris's RER A suburban line in 1989.
Additional deployments encompass:
- Santiago Metro in Chile;
- Various MTR lines in Hong Kong—including Kwun Tong, Tsuen Wan, Island, Tseung Kwan O, Airport Express, and Tung Chung—all equipped with Automatic Train Operation (ATO);
- Mexico City Metro Lines A, B, and 8; and
- Shanghai Metro Line 3.
In 2017, SACEM on the Paris RER A underwent an upgrade incorporating Automatic Train Operation, becoming fully functional by the end of 2018.
Looking ahead, Paris intends to transform SACEM into a comprehensive Communications-Based Train Control (CBTC) system called NExTEO. This upgrade is planned for initial rollout on the extended RER E line in 2024 and is designed to supplant existing signalling and control systems across all RER routes.
Operation
SACEM allows trains to obtain signals transmitted from trackside equipment. An onboard receiver processes these signals and presents them on the driver’s console, where an orange indicator denotes a reduced speed requirement () and a red indicator commands a complete stop. Should the train operator surpass prescribed speed thresholds, an audible alert is activated; if speed reduction is not achieved promptly, the emergency braking system engages automatically. This technology diminishes train congestion and supports efficient recovery from delays, enabling increased service frequency during peak periods.