Passenger rail systems can share freight lines. Japan does it all the time. It was done in this country for over a hundred years until competition with the Federal Highway system killed the railroads. Europe has a vast network of canals where most of the freight is moved. Railroads in Europe always mostly moved people and time sensitive freight.
They can and sometimes do, but for our system, it's not the best solution.
Many Class 1 and most Class 2 rail line systems in this country are privately owned. Most passenger lines are publicly owned (to a majority extent). In addition, our freight line systems are very active. Japan has a much smaller active system -- similar to Europe. The vast majority of Japanese systems are -- again like Europe -- passenger focused.
We do have systems that share lines, but very few. Positive Train Control (PTC) was envisioned to prevent accidents like the 2008 Chatsworth train collision, but while it has been authorized by congress, it has not been implemented in any real way system-wide. The Chatsworth collision involved a Union Pacific freight train colliding with a Metrolink passenger train and caused the death of 25 people and 135 injuries. The cause was due to an engineer texting and ignoring a red signal. The result of this collision was the Rail Safety Improvement Act -- legislation I was heavily involved in.
We have a long ways to go before we are ready for shared lines between passenger and freight, and a long ways to go before we see real movement in passenger rail overall.
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