In the six months since the EPA revealed that Volkswagen used illegal "defeat device" software on TDI diesel cars, there have been many suggestions about how the company should pay for its deception.
VW will of course have to recall all of the nearly 600,000 affected cars in the U.S.
It also faces hefty payouts for both civil suits and potential government fines.
But on top of that, some have suggested that Volkswagen buy back at least some of the affected cars, or even be forced to build more electric cars as penance.
Now, there's another idea.
It comes from the Union of Concerned Scientists (UCS), which believes Volkswagen could be forced to fund programs that clean up the dirtiest diesel trucks.
Freightliner Inspiration Truck self-driving truck concept
Admittedly under some pressure from the diesel scandal, Volkswagen has already committed to produce more electric cars, even introducing a dedicated platform called MEB.
And in California, VW is already mandated to sell zero-emission vehicles, as are all carmakers whose sales in the state are at certain levels.
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Instead of a "punishment" that would also help Volkswagen sell more cars, the UCS advocates using the company's money to fund environmental initiatives.
It believes regulators should focus on heavy-duty trucks, because those are among the highest-polluting vehicles on the road.
They account for a disproportionate amount of emissions, in part because they cover more mileage than passenger cars annually.
Daimler Trucks North America SuperTruck
This could be done along the lines of the Diesel Emissions Reductions Act, and help encourage replacing dirtier trucks or retrofitting them with emissions-reducing equipment.
There could even be provisions for zero-emission trucks, notes the UCS.
Some solution other than a recall may be necessary, the proposal's author notes, because not every car may be addressed.
Volkswagen still hasn't gotten a plan approved to fix every affected TDI model.
And some of the older cars may require expensive modifications, such as the addition of exhaust aftertreatment systems, that may not make financial sense.
Natural Gas-powered Kenworth truck (Image: Flickr user TruckPR)
That would be convenient for VW, but whether it will be sufficient for scores of frustrated owners and environmental advocates is unclear.