"In cities which" or "In cities where"

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1

<p>This bothered me recently after doing a improving sentence error in pg 479, Q 19:</p>

<p>In those cities in which public transportation is adequate, fewer traffic problems occur and pedestrians are rarely involved in accidents.</p>

<p>There is no error in this sentence, but I was wondering if it was possible to say "in where".</p>

2

<p>it would be possible to say just "where" by itself, but "in where" wouldn't be correct.</p>

3

<p>it's... correct, but if "where" was a possible answer i'd have picked that.</p>