 Amtrak took over most intercity passenger service on May 1, 1971.However, the Denver and Rio Grande Western Railroad (D&RGW) opted to continue to privately operate its "Rio Grande Zephyr".In 1983, facing heavy losses, the D&RGW agreed to allow Amtrak to reroute the "San Francisco Zephyr" over its Moffat Tunnel Route mainline.