Yes, narrowing lanes will increase drivers' stress (whether by a significant amount, I don't know). But it will also decrease the stress of cyclists, pedestrians, and other people using the same roads. So this is not a straightforward consideration against narrowing lanes, or any other measure that will increase safety but increase drivers' stress as a side effect. To me, it sounds like a good trade: when the stress of driving goes up and the stress of cycling or walking goes down, more people will switch away from driving, and there are many reasons why that would be a good thing.
Actually will narrowing lanes increase driver stress?
Presumably, the increased stress is why they drive slower in the first place, which should then have a canceling effect lowering their stress back to the original level.
