The line to pay for parking at the sixth street garage is very long during peak hours. If you are not going to have two cashiers available to handle the volume, please install self-pay credit card stations to shorten the wait time. Also, a pay station on the east side of the garage will benefit those parked on the east side, since your cashier booth isn't located in the middle.
Update: CatPAD "Pay & Dash!" stations have been installed in the 2nd Street Garage. Main Gate and Sixth Street garages will see these stations in the fall, with the remaining garages soon after.
Thanks to David Heineking, Director of Parking & Transportation for the following response:
We are trying. PCI requirements (the rules that govern security of credit cards) are very onerous. We are working our way through this process. You should see these pay stations soon.
(Response May 2014)