This past December ACE completed our last phase of installing (PTC) Positive Train Control on ACE equipment. PTC is a federally mandated safety system. With the implementation of PTC we have been having some technical issues that have caused delays to the service. ACE and our partners have been working to resolve these issues and we should see a reduction and elimination of delays related to the system soon. We understand the importance of arriving on time to your station and we will continue to work on providing reliable and safe service. Thank you for being a loyal ACE rider.

As well, if you want to know more about PTC, Union Pacific actually has a really nice breakdown of everything involved here: https://www.up.com/media/media_kit/ptc/about-ptc/