I have messed about on GMSV more times than I care to mention, and from going through street view on mainline and ramp toll plazas on toll roads using a ticket system (e.g. Indiana Toll Road, New York State Thruway, PA, OH, NJ, KS turnpikes,) I have noticed that there are (usually) more lanes for exiting traffic than entering (although with some it looks balanced.)
Why do you think this is?
Takes more time to hand over a ticket and cash (and potentially receive return change) than it does to just receive a ticket.