No, its almost impossible for any type of commuter rail.....long distance, yes maybe, but not with commuters.
If they have to get screened at the train station every day for 5, 10, 15 minutes, they are giong to drive and get to work other ways. Not to mention the "Just In Time" arrival at the station get tehre, run down stairs to the train. Most commuters don't wait at the station for a particular train, they get on the next one or the fastest one (not necessarily the next trian leaving though) to their destination.
Also, the thousands of people that rush in and out of a station during rush hour in mere minutes would simply create a people gridlock and no one would be able to move with people waiting to get screened. The compacting of people more and more by slowing down the flow would only make that location an even more desireable target because of the increased number people that are in that location (trapped basically and possibly creating a crowd/riot/stampeede problem)
Anyway, metal detectors and things like that are not doing anything to guard against the outside of the terminal/station the streets above the station (permamently close 8th ave in NYC because it passes over the station? = can't do that!!!) and all the outlying stations where people get on the trains with no security at all.
"invisible" security IMO is the best deterrant and measure that the agencies can do. Undercover police, detectors of various germs/poisons/radation, etc, intelligence all coupled with a police presense in the locations is once again, in my opinion, the best that we can do, and the most realistic and practical.
On the RR, "believe nothing you hear and only half of what you see"
John, aka "JTGSHU" passed away on August 26, 2013. We honor his memory and his devotion to railroading at railroad.net.