It's not Bernoulli mainly that factors into this, it's Boyle.

Pressure dynamics is the same whether it's for gas, liquid or even traffic
patterns.

Reduce the size of the pipe, duct or road and you increase the pressure and
reduce the velocity.

So the idea that a reduction at one point (be it the smaller pickup at a saw or
a roadblock in the middle of the road), the pressure increases, the dust, car,
water, whatever slows, but then, as the pressure decreases with the increase in
the roadwork, the speed increases.

The traffic analogy was not mine, but worked out by some highway engineers.
They were surprised to learn that traffic flow basically obeys Boyle's law.

Which is why you want large main ductwork, this is your freeway. The smaller
gates are your on ramps.

The speed cannot be the same throughout. Just as traffic picks up after a
slowdown. Sometimes when you hit traffic and then it speeds up, you wonder why.
Well, there was a stoppage a while ago, and the system is simply recovering. It
does not stay slow the entire way.