As railroads have continued to evolve and large Class I railroads have sought to keep cars on line (as well as collect the revenues for the tonnage moved over their own route miles), most bridge lines are now gone.
[3] The most recent example of a "bridge" carrier being swallowed up was the Wisconsin Central.
The WC was a bridge line for Canadian National's traffic out of Chicago to western Canada.
Once CN had integrated its purchase of Illinois Central, there was no route for it to send trains to points in western Canada on its own rails.
Eventually, CN bought the WC outright and integrated the line into its system, rather than pay the carrier to move its freight.