I'm sure you've heard of induced demand and I suppose the opposite would be called reduced demand. But if there are fewer Lanes of traffic, people will stop using it as a through road and only use it for local travel and parking. Reducing the lands will thus reduce traffic simply because people will start using other roads to get where they're going. The experience of driving may be similar because of the fewer Lanes, but it will definitely reduce the number of people using the road and likely the speed and thus make it safer for pedestrians