The "Cardinal" is one of only two of Amtrak's 15 long-distance trains to operate only three days a week, the other being the "Sunset Limited". Like other long-distance trains, passengers are not allowed to travel only between stations on the Northeast Corridor on the "Cardinal". Eastbound trains only stop to discharge passengers from Alexandria northward, and westbound trains only stop to receive passengers from Newark to Washington. This policy aims to keep seats available for passengers making longer trips; passengers traveling between Northeast Corridor stations can use the more frequent "Acela Express" or "Northeast Regional" services.