A voluntary road pricing scheme could win the backing of motorists and cut congestion, according to a West Midlands MP.
Solihull MP Lorely Burt (Lib Dem Solihull) supported calls for voluntary charges at the Liberal Democrat conference in Brighton.
Drivers would choose to opt into the scheme, and receive discounts in return.
They would pay less fuel duty at petrol pumps, and could also enjoy free break-down cover.
The proposals, based on a scheme already operating in Oregon, in the US, have been drawn up by charity the RAC Foundation.
Ms Burt, a Lib Dem business spokeswoman, backed the idea when she took part in a discussion on road pricing.
She said road pricing would continue to be a high-profile issue because drastic action was needed to stop traffic congestion growing even worse.
However, recent bad publicity, including a petition against pricing signed by 1.6 million people, had made the idea of charges unpopular.
She said: "If road pricing is ever going to be accepted by the British public then it has to be on the basis of the benefits it will bring.
"If it's just about paying more money for driving then it is never going to be accepted.
"Making it voluntary is a good way to go. You will get a few people who are keen to try it out and then it will spread.
"It takes a lot of the fear out of it, because people will know they can opt out again."
Drivers who chose to take part in a road pricing scheme could receive a dis-count on fuel duty at petrol stations or be exempt entirely, she said.
"Road pricing is potentially the biggest political hot potato of the next 10 years," she added.
The Liberal Democrats back road pricing in principle, as long as the money raised is no more than motorists currently pay in fuel duty and road tax.
The party also believes there should be safeguards about how information about vehicle movements will be used, to avoid infringements of privacy.
Ms Burt said: "The Government has done a very poor job of selling the idea to the public. People understandably want to know how a scheme will work and how much it will cost, but Ministers still don't have any answers."
The RAC Foundation has called its proposed voluntary scheme "UK DriveTime".
West Midland councils have decided not to apply to run a pilot road pricing scheme in the immediate future.
The seven councils, and passenger transport authority Centro, held back from responding to a Government request to submit proposals for road pricing and congestion charging.
Despite an 18-month study costing £4.1 million, the councils have yet to agree on whether or not to introduce a pricing scheme.
Meanwhile, Greater Manchester authorities have launched a formal bid to the Government to introduce charges and could receive up to £2 billion for public transport improvements as a reward.
Shrewsbury County Council is planning to introduce a smaller pricing scheme.