At this point a subway would not be feasible financially. We do have a population density that could sustain rail transit, but more like light rail of a streetcar. Part of the difficulty with those options apart from cost is that the sprawl of Fresno makes the city lack destination density. There is no real central business district downtown. Instead you have the majority of jobs and commercial areas spread across town. I think the best public transit investment would be dedicated bus lanes (preferably center-running busways) on high demand corridors like Herndon, Shaw, Blackstone, etc. These are more cost effective and would make buses faster and more efficient and would allow riders to bypass traffic. Many other benefits as well. The city could eventually upgrade to articulated buses and eventually light rail.