Abstract
Since the early years of railway electrification, 3rd rail conductors have evolved from steel to aluminum/steel composite to aluminum/stainless steel composition. Aluminum stainless steel (ALSS) conductors are currently in use in approximately 75% of the nearly 20,000 km of 3rd rail systems worldwide and continue to gain acceptance by North American transit authorities.
Electrical efficiency improvement with ALSS ranges from 1.6 to 2.5 times that of steel aluminum and steel rails. At 33% of the weight of steel rail and 60% of aluminum-steel composite rail, ALSS offers considerable costs-savings in freight, handling, and installation. Though electrical efficiency and light weight are among the more widely known benefits of ALSS 3rd rail, durability has significantly improved since the introduction of ALSS technology in the late 20th Century.
The implementation of signaling technologies such as CBTC has enabled increased train throughput; however the lack of necessary available power (voltage) to support these headways can be a limiting factor to capacity improvements. Upgrading legacy 3rd rail to ALSS is a cost-effective means of increasing available power with minimal disruption. Drop-in replacement profiles of ALSS 3rd rail have been developed for several common legacy profiles to include 150lb steel and 85C, facilitating replacement of existing 3rd rail.
This paper examines the technical and economic aspects of aluminum/stainless steel 3rd rail and its adoption by several North American transit authorities. The author explains the characteristics, benefits and limitations of aluminum stainless steel 3rd rail with comparisons to legacy steel and steel-aluminum power rails.
