The nation's highways were in poor shape to handle this increasing load of traffic. Little had been done during the war to improve the highways，and war-time traffic had exacerbated their condition.

The nation's highways were in poor shape to handle this increasing load of traffic.
①全米の(幹線)道路は、この増え続ける交通量への対処が難しくなっていた（処理できないほど老朽化していた）。

Little had been done during the war to improve the highways，and war-time traffic had exacerbated their condition.
②戦時中は、(幹線)道路の改修が殆ど行なわれず、そのうえ戦時下の交通は(幹線)道路の劣化に拍車をかけた。

Moreover, the growth of development in the suburbs occurred where highways did not have the capacity to carry the resulting traffic. Suburban traffic quick1y overwhelmed the existing two-lane formerly rural roads (U.S. Dept. of Transportation, 1979a).

Moreover, the growth of development in the suburbs occurred where highways did not have the capacity to carry the resulting traffic.
③さらに、郊外地域での開発は、(幹線)道路(の交通容量)がその誘発交通を捌けられない場所で行なわれた。

Suburban traffic quick1y overwhelmed the existing two-lane formerly rural roads (U.S. Dept. of Transportation, 1979a).
④郊外交通は、既存の2車線の古い地方道をすぐに圧迫した。(USDT、1979a)