Bentley Rail Track does have a Swept Envelope Analysis command. This command creates swept envelopes for rail vehicles. The swept envelope is created as do not triangulate features/components in a DTM and displayed as a mesh in MicroStation. To activate this dialog select the Swept Envelope Add-In on the Tools > Applications Add-Ins menu. The command itself is located in Modeler > Swept Envelope Analysis.
Please take a look at this command and let me know if it will meet your needs.