The use of the self-release option may allow motorists to get their cars back quicker than waiting for a city worker to come unlock the boot, and the mayor could be figuring that many drivers will be willing to pay the additional "boot release fee" in exchange for the convenience. That would be similar to the credit card payment option now in place for Chicago parking meters, where drivers can add time remotely, but there is a 35-cent convenience fee that goes to meter operator Chicago Parking Meters for each transaction of less than two hours.