For the rugged Railway environment, CompactPCI Serial and MicroTCA are backplane-approaches that are commonly used. They provide high-performance real-time control in a ruggedizable, scalable, and modular solution. They are also used in railway communications and dispatch systems. A wealth of module options have been developed for Railway for over 20 years for CompactPCI and more recently for CompactPCI Serial.
COM Express offers a compact and scalable mezzanine-based approach with rugged connectors and design implementations in the market. These three specifications are also used in traffic control and toll booth systems, deployed in IP66 or other weather-proof boxes or ATRs that survive extreme temperatures and environments. COM Express is a particularly good fit for the applications that require a small form factor, such as Automotive, Trucking, etc.
Other Transportation applications include Trucking, Avionics, Automotive, and more. See the Military/Aerospace page for more on Avionics.