The limits are by value. You’ll have to enter your PIN for transactions above £45 - but this is nothing new. You will now also have to enter your pin once you reach a cumulative amount of consecutive contactless transactions totalling over £225.
There will be some exemptions to this - most unattended payment terminals won’t ask you for your PIN and you’ll be able to pay through contactless as many times in a row as you like. This means you can carry on using TFL as normal!