As a country America has the most advanced economy and t-echnology and ever dropped behind in the fields of ITS studying. Now they have hold the first place not only in theory reach butalso in applying.

• 作为经济发达、技术先进的美国，虽在 ITS 的研究开发上曾一度落后，但凭借其先进的技术优势，已后来居上，目前在试验研究和实践应用上都处于领先地位。