Difference between Blind Alley and Cul De Sac

BLIND ALLEY vs CUL DE SAC: NOUN

A course of inquiry that leads nowhere.
Used other than as an idiom: see blind,‎ alley. A street or passageway that leads nowhere.
A mistaken, unproductive undertaking.
An alley or passage that is closed at one end.
A street with only one way in or out
(figurative) a course of action that is unproductive and offers no hope of improvement

Circumlocutionary, Miswander, Pointless, Unfruitfully, Meander, Meanderingly, Pererration, Fruitless, Longspun, Tedious, Aimless, Dead end street, Impasse, Dead end, Cul de sac

Standstill, Stand off, Stalemate, Road, Logjam, Lane, Inside, Impasse, Gridlock, Deadlock, Dead end

Circumbendibus, Vagous, Circumlocutionary, Miswander, Pointless, Unfruitfully, Meander, Meanderingly, Pererration, Fruitless, Longspun, Tedious, Aimless, Dead end, Cul de sac

We must learn from the masses constantly if we do not want to lead them down a blind alley.
If you go down a blind alley you can always backtrack.
Bush administration which had led the United States up a blind alley in Afghanistan and Iraq.
Automatic control of pitch is (in my experience and opinion) a blind alley.
Loneliness can lead to a blind alley in which masturbation becomes an addiction.
In the absence of any contrary evidence, this is a blind alley.
One natural starting point leads down a blind alley.
But that turned out to be a blind alley.
This road has soon led into a blind alley.
Even if you can see instantly that a blind date is a blind alley, stick around for a couple of drinks at least.

Internationalisation or Isolation: The Australian Cul de Sac?
But that can be a cul de sac.
Delightful accommodation in a quiet cul de sac.
PERFECTLY PLACED IN TIMBER TRACE CUL DE SAC!
Cul De Sac, Newer Yorba Linda High School.
Magnificent view property on quiet cul de sac.
Fantastically quiet location in a cul de sac.
LOT IS LOCATED IN A CUL DE SAC.
Transportation infrastructure is created by burrowing into the center of each cul-de-sac (sprawling in) and linking to other cul-de-sacs via a subterranean street grid.
The first and last (the cul-de-sac start and finish) are controlled by the level of the cul-de-sac road.