"as long as" versus "until"

[Lopez]

English Language Tests, Intermediate level

ESL/EFL Test #142 "Time clauses: future tense examples", question 8

Don't cross the road ......... you see the green man.

(a) as long as
(b) as soon as
(c) while
(d) until

English Language Tests, Intermediate level

ESL/EFL Test #142 "Time clauses: future tense examples", answer 8

Don't cross the road until you see the green man.

Correct answer: (d) until
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Why not "as long as"?

Lopez

[Mister Micawber]

.
As long as roughly means during; therefore, you would indeed cross the road as long as you saw 'the green man' (the lighted icon indicating that pedestrians may now cross).
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Native English teacher at Mister Micawber's