Thousands of freight firms operating in London have not applied for new safety permits required to avoid daily £550 fines.
Transport for London (TfL) said 50,000 permits aimed at reducing blind spots from HGVs have been issued but urged more companies to apply before enforcement begins in less than six weeks.
Vehicles are given a rating of between zero and five stars based on how much the driver can see through their cab window, and the subsequent level of risk to vulnerable road users. A minimum of one star will be required from March 1, rising to three stars by 2024 subject to consultation.
Enforcement of the Direct Vision Standard (DVS) was due to begin in October 2019 but was postponed to give affected businesses more time to prepare.
The new rules will apply to all lorries deployed in London, whether they are registered in the UK or overseas.
Vehicles which do not meet minimum vision standards must have safety measures such as blind spot cameras and audible alerts for turning left retrofitted. The use of permits will be enforced by number plate recognition cameras. Non-compliant HGVs will be issued with a penalty charge notice of £550 per day if they are driven in London, which will be reduced by 50% if paid within 14 days.
The DVS is part of London mayor Sadiq Khan's Vision Zero ambition to eliminate deaths and serious injuries from London's transport network by 2041.
HGVs were involved in 15% of fatal crashes in the capital between 2018 and 2020 despite making up just 3% of vehicle traffic, according to TfL.
This includes 41% of collisions where a cyclist was killed, and 19% of those with a pedestrian fatality.
London walking and cycling commissioner Will Norman said: "Our world-leading Direct Vision Standard will remove the most dangerous lorries from our city's streets and save lives.
"With record numbers of Londoners walking and cycling as a result of the pandemic, it's vital that we do all we can to protect them. "I urge all HGV operators to apply for their safety permits as soon as possible as there are now less than two months to go until enforcement begins."
Paul Abbott, group director at logistics firm Knights of Old Group, said the introduction of the DVS "allows the industry to further demonstrate their commitment to do everything in their control to maximise driver vision and awareness".