Hahahaa, sorry, I did not mean to bash you. Also I respond late because I do not visit the site often as I am very busy and thus short on time.
I just wanted to point out the confusion and logical fallacy in your statement. There are a lot of implicit premise in your statement which leaves a lot of question unanswered which can only be surmised with readers' own assumptions filled in. The most glaring question is the following. You said "大华府地区的富贵社区仍然没有地铁". The fact that "潜在罪犯只在自己的东南部社区相互对射,他们并不乐意花上一个小时,坐地铁来到西部或北部去打枪或抢劫。" could be due to that it is not worthwhile to rob a not-so-rich neighbourhood with one hour's travel. That leaves the great possibility that had the subway been constructed through the richer area, it would have been more than worth the travel, greatly aided by the convenience of the subway, to rob the rich. Hence, your conclusion "这种担忧被证实是不必要的" does not stand logically, and has not "被证实".
I agree with 清漪园 on this point. Gun violence in poor neighborhood usually happen between criminal gangs who have no reason to travel to remote suburbans to fight.
however, the lack of public transportation does prevent people from finding jobs, which partly explains why so many people from those communities are on welfare.
Your deduction process is not clear. You acknowledged "大华府地区的富贵社区仍然没有地铁,连道路都是对开的弯曲小路". How does the fact that the subway is not built lead to the conclusion "这种担忧被证实是不必要的"? Can you explain your logic?
大华府地区也曾经是一个种族隔离的城市,有色居民多住东部与南部,白人亚裔则多住西部与北部。这里的老住户告诉我,70年代修地铁时,Georgetown, Great Falls 等富裕的白人区出于雅美兄所提到的同样的担心,拒绝让地铁穿行。但是,这种担忧被证实是不必要的,潜在罪犯只在自己的东南部社区相互对射,他们并不乐意花上一个小时,坐地铁来到西部或北部去打枪或抢劫。在西部和北部的罪犯,多是住在当地的居民。