Your iPad's offline functions are available anywhere you are, as long as your iPad has power. Your functions that depend on Internet connectivity will vary according to your specific train, location, iPad model and data plan, just as it would in a car or any other ground-level moving vehicle. Generally, you will receive better Internet service on your iPad in major metropolitan areas than in remote areas, but this is not always the case.
If you have a Wi-Fi only iPad or prefer to use Wi-Fi instead of 3G, check the specific information for your train when you book your trip or on the train service's website. As of July 2011, Amtrak offers Wi-Fi service on the Acela Express and Amtrak Cascades trains, as well as the Pacific Parlour car on the Coast Starlight train. In Canada, VIA Rail offers Wi-Fi on most trains in the Quebec-Windsor City corridor. Both train systems offer Wi-Fi service in select train stations as well.
The Wi-Fi networks offered on trains are shared with all other passengers on that train, so your Internet capabilities and speed may be less than you are used to on the iPad. Amtrak and VIA Rail ask that passengers limit their Internet activity to e-mail and browsing Web pages as the system cannot handle video streaming or large downloads. This means you can use your "Mail," "Safari," "Maps" and other Internet-enabled iPad apps, but should not attempt to download items from iTunes or the App Store or access large files from cloud storage apps.
Wi-Fi + 3G iPad models have a better chance of getting Internet service along many train routes because you can connect to the AT&T or Verizon cellular networks, which cover more areas than public Wi-Fi hotspots. Only AT&T's network will work for AT&T iPads, and only Verizon's network will work for Verizon iPad models, so consult the coverage map for your specific carrier to get the most accurate coverage information. Expect to have gaps in service even if your provider seems to cover your train route, as the motion of the train through mountains, trees and other structures can block signal in some areas.
The iPad features a 10-hour average battery life, and this can be extended or reduced according to how you use it. Many trains offer power outlets in the sleeping cars, but you may not have access to recharge your iPad in all areas. If you plan a trip more than 10 hours and do not have access to a power outlet on the train, you can conserve battery life by turning off Bluetooth and cellular data functions when you are not using them. Close any apps that may use frequent Internet updating, such as maps that track your location.