Generally, no, you cannot use an InterCity (IC) ticket to board an InterCity Express (ICE) train because they belong to different price categories. In Germany’s Deutsche Bahn system, tickets are usually valid only for the specific type of train or lower (e.g., an ICE ticket can be used on an IC or regional train, but not vice versa). However, there is a major exception under European passenger rights: if your original IC train is delayed by more than 20 minutes, or if a delay means you will miss your destination by more than 20 minutes, your ticket becomes "flexible." In this specific case, you can board an ICE to complete your journey. You may be required to pay the price difference upfront to the conductor or at a machine and then claim it back later through the Fahrgastrechte (Passenger Rights) process. In 2026, with the Deutschland-Ticket costing €63, it is important to remember that this local transport pass is strictly for regional trains and never allows for IC or ICE travel, even during significant delays, unless the railroad explicitly announces an exception for a specific disruption.