Caltrans and many of my transit operators had/have very bad GIS data on the locations of loops, sensors, signals, and things like bus stops.

I have seen various grade crossing lists that lead me to the same conclusion. There are also thousands of abandoned crossings, as well. As many as two hundred in and around downtown LA from what I observed from the Alameda Street study several years ago.

For a while, in the late 90's and early 2000's I found myself constantly driving to locations with a GPS ball on my truck, and a laptop, entering data. And, it is a lot of work.

I regularly loaned this out to transit agencies, who found that hiring interns, and driving around with a gps antenna and collecting new data was "faster, better, cheaper" than trying to "fix" the bad data, that had accumulated over the years, often in different formats, programs, or coordinate systems.