There must be pollution wherever the power is made that it takes to compress that air to start with, either diesel or electric, or???
There is no free lunch, a compressed air car still has emissions (don't know what % of a regular car?) they are just in a different place from where the car is driven.

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-