| Clue | Source | Date |
|---|---|---|
| See 5-Down | New York Times | 22 May 2022 |
| Octagonal warnings | Eugene Sheffer | 08 Mar 2021 |
| Corner quartet, perhaps | LA Times Daily | 24 Apr 2020 |
| Corner quartet, perhaps | The Washington Post | 24 Apr 2020 |
| Intersection quartet, maybe | USA Today | 12 Jul 2018 |
| Intersection quartet, maybe | ||
| Red alerts | ||
| Red alerts | ||
| Corner octagons | ||
| Roadside octagons | ||
| Urban halters | ||
| These are usually octagonal | ||
| Special notices for motorists. |