Hmmmm.... Lot's of luck to NJ Transit trying to implement such a policy.... If you've ever ridden the 6:16p to Dover out of NY Penn, OMG! The outer vestibules are crawling with people. The only thing the conductors don't allow in that case is letting people ride right at the connection point between the two cars. That, and they try to keep the e-brake point clear in the car the break man would have to use in such a situation. But, otherwise, that train was regularly a zoo. It was so bad that the conductors would often just not bother to collect fares on that trip. Which sucked for those who bought monthly passes, etc. It was Alannis Morrisette's "Free ride when you already paid" IRL.
Hopefully, it's better now with the double decker cars and the ALP-46's.