Technology

And next year the congestion will be the same as before, except with even more cars and even more emissions.

This is equivalent to building another lane on a highway to increase throughput and decrease traffic jams. In the beginning, emissions will be reduced since traffic jams occur less frequently. And then, through induced demand, there's congestion again.

Improving car throughput directly leads to increased emissions with a small delay.

From the paper:

Increased speeds from adaptive signals may induce additional travel, as people opt to drive more or travel farther, potentially offsetting some congestion benefits. Our models do not fully capture induced demand due to data limitations, but adaptive signaling generally supports higher traffic volumes and smoother flows.