The Freight Transport Association (FTA) has said it is disappointed to hear that the introduction of free-flow tolls at the Dartford River Crossing between Dartford and Thurrock will be delayed until late November.

Work had been expected to have finished by the end of October, but the Highways Agency recently revealed that the installation of the new technology cannot be completed for at least another four weeks.

Free-flow will allow drivers to use the crossing without having to stop at barriers to pay. Instead, they can pay the charge by phone, text or at retail outlets, speeding up the whole process and meaning drivers won't have to worry about carrying cash.

The changes are costing between £48 million and £62 million, but have been deemed necessary because the crossing now sees around 50 million vehicles every year. This is resulting in significant congestion and delays.

Once the Dart Charge has been brought in, further work will be carried out to remove the existing payment booths and change the road layout by spring 2015.

Now, the FTA has criticised the delays to the project's implementation, with head of road network management policy Malcolm Bingham saying it will result in additional costs to business drivers in particular.

"The costs of this hold-up are unacceptable to the freight industry. FTA has been asking for a long time for this system to be introduced," he added.

Indeed, it is estimated that it costs an estimated £1 per minute per HGV in running costs to queue at the Dartford tolls.

"FTA has and will continue to work with the Highways Agency to help get a resolution to this issue as soon as possible," Mr Bingham added.

The crossing is situated around 16 miles east of London and forms a trunk road link in the M25 London orbital motorway, an important gateway to the ports on the Kent and Essex coasts.

Road User Charges were implemented there in 2003.