Signal dream meaning is explained below using 6 different sources. Each interpretation is shown with its source.

Interpretation 1 — Zolar

lucky numbers: 04-20-27-35-43-47

danger, a: conditions are unfavorable to an improvement in your affairs.

overlooking a: wil struggle to humor your pride.

hearing a fire: wil be informed of unpleasant happenings.

police: wil be cheated by a woman but wil gain in some other pursuit.

of a, station: be cautious to protect the integrity of your system.

red light, a: are placing your life in dangerous hands.

seeing a, but not heeding it: misfortune of friends wil depress you.

semaphore, a: warning of emotional trouble; the competition is not yours.

alphabet flags: state your case; if they don’t accept it,move on.

street, a: contagious diseases wil confront you.

officer directing traffic at a: the competency is yours and can’t be shared.

woman dreaming of a police siren: be cautious whom you let approach you familiarly.

Source: Zolar’s Book of Dreams Numbers and Lucky Days Author: Zolar

Interpretation 2 — Stearn Robinson - Tom Corbett

The meaning of this dream varies considerably according to the details of its action, but as a general guide, signals represent the realization of long-delayed wishes or ambitions.
Source: The Complete Guide to Interpreting Your Dreams Author: Stearn Robinson - Tom Corbett

Interpretation 3 — Internet Archive - Anonymous

Waiting in a station for a train that is Signalled, is a portent of long delayed wishes that will at last be realised.
Source: Mystic Dream Book Author: Internet Archive - Anonymous

Interpretation 4 — Garuda

Vision: Hearing a signal is a warning about impending events or certain people.

See Bell, Whistle.

Source: Dreamers Dictionary Author: Garuda

Interpretation 5 — Klaus Vollmar

Advice and help.
Source: Little Giant Encyclopedia Author: Klaus Vollmar

Interpretation 6 — Margaret Hamilton

See “sign”
Source: Dream Dictionary Unlimited Author: Margaret Hamilton