May I suggest a letter something like this:
I am writing to urge you please to make sensible decisions regarding transportation in the upcoming stimulus package. Mass transit and high-speed rail project fund must not be raided for further road building. In addition, highway dollars should be channeled toward repair and maintenance. This will increase safety, provide jobs, reduce the growth of sprwal, and reduce future expenses in maintenance and repair. By contrast, new road project, while they do allow for ribbon-cutting and pork boasting, only increase future maintenance burden and encourage sprawl and therefore petroleum dependence. Please resist the political expedience of new highway projects and emphasize our existing infrastructure.
You can find your representative here and your senators here.