Doubts have been raised about the cost-benefit ratio of the pilot project. Micheal Kraft, vice president of the Hessian Motor Trade Association, considers the technology, which is already used in Sweden, to be uneconomical.
If something is uneconomical, it simply cannot work unless it is subsidized and then the question is whether there isn't a better use for that money. Cost-Benefit is always relevant. If you just care about the health effects, subsidizing gas-powered vehicles may be more cost efficient.
Or alternatively, everything else is made worse. Raise taxes on Diesel, raise taxes on non-hybrid and non-electric trucks, forbid non-electric trucks from autobahns, etc.
If you are a government, you don't have to make this solution better, you can just make all other solutions worse.