Dead End signs warn drivers that the road they are on ends in a dead-end or cul-de-sac. Posted at the entrance of dead-end streets/roads, these signs alert motorists that the street/road will not connect to another street/road, thereby avoiding traffic commotion and saving time.
These signs are important also because they give motorists the opportunity to slow down on dead-end roads well in time before reaching the end of the road.
Dead End signs indicate that the road or street terminates in a cul-de-sac while No Outlet signs communicate that there is no other exit to a cluster of roads. Where Dead End signs are used on single streets, No Outlet signs are usually used on streets that connect to one or more streets in a neighborhood but have a single point of entry and exit.
In practice, many public works departments prefer to use No Outlet signs even for dead-end streets, as indicated in this report about the practices prevalent in Washington.
Standards and guidance regarding Dead End signs and No Outlet signs are provided in Section 2C.26 of the MUTCD. The section defines when these signs may be used and where these should be placed. Four types of signs are described in the section — W14-1, W14-1a, W14-2, and W14-2a — the design specifications of which are covered here.
While both dead-end and cul-de-sac imply a street that leads to nowhere, i.e., has no outlet, these differ in how the street in question terminates. Where a dead-end street just terminates abruptly, a cul-de-sac usually has a circular ending that lets vehicles turn around easily without having to maneuver a tricky and often sharp u-turn. In a nutshell, all cul-de-sacs are dead-ends but not vice versa.