Drivers who breach the rules of London’s expanded ultra low emission zone (Ulez) may initially be warned rather than fined.
Transport for London (TfL) told the PA news agency it can use its “discretion” to issue warning letters instead of penalty charge notices (PCNs).
The AA said it is “essential” that drivers are not fined “until the system beds in” across the new Ulez areas.
From August 29, the Ulez scheme will be expanded from the North and South Circular roads to cover the whole of Greater London.
People who drive in the zone in a vehicle that does not meet minimum emissions standards are required to pay a £12.50 daily fee within three days.
Failure to pay can lead to a PCN of £180, reduced to £90 if paid within 14 days.
TfL has sent letters about the expansion to the owners of non-compliant vehicles previously detected by cameras in the new Ulez area.
But some affected motorists may drive in the zone without knowing they are required to pay a fee.
There are fears that the refusal by some neighbouring counties to allow TfL to put up signage on roads approaching the new Ulez area could also lead to people entering it by mistake.
TfL said in a statement: “TfL reserves the right to use discretion to issue a warning notice instead of a penalty charge notice.
“However, we would advise anyone driving a non-compliant vehicle in the zone to pay the charge to avoid the risk of being fined.”
There are various methods of paying the Ulez charge, including online, over the phone, through an app or by signing up to an automatic payment system.
AA president Edmund King said: “It is essential that TfL sends out warning letters to drivers not complying with the Ulez until the system beds in.
“We know that there is a widespread lack of signage outside the current zone in areas such as Hertfordshire, so fining drivers who don’t even know they are in the zone would backfire.
“Drivers need fair warning of when they are about to enter the Ulez or when they are on a road that will take them into the zone if they stay on it.
“If TfL do not send out warnings they will be deluged with complaints from drivers.
“If they turn down appeals to have fines cancelled, huge numbers will take their complaints to the traffic penalties tribunal.”
On the day that Birmingham’s emissions-based charging scheme was introduced in June 2021, the city’s council announced that the £8 daily fees for non-compliant vehicles would not need to be paid for the first two weeks as part of a “soft launch”.