Instead of filling in the green visa waiver form en route, short-term visitors must register their details online at least three days before they depart.
Back in April the U.S. government started questioning the viability of their plan to use RFID chips to store biometric data in passports, which would also have required biometric passports from any visitors to the U.S. entering the country under the Visa Waiver program (which allows short-term visits without a visa).