What does 'trade in' mean in this article on the Westway project?

Question

A little background so you know where we are at. I'm doing a paper concerning the Westway project* specifically the period immediately before the collapse of the project in which hundreds of individuals rallied to bring down the project on grounds of environmentally (and other) detrimental effects.

There is an article in the New York Times (1982) stating:

"At the end of 1981 the value of the trade-in was estimated at $1.2 billion. But that money would not come from the [Federal Highway Trust Fund]; Congress would have to dip into general revenues. It now has a backlog of $5.7 billion in already approved trade-ins, yet has been appropriating only $800 million a year." [For westway, yet again. (1982, Mar 26). New York Times (1923-Current File).]

I have a few questions.

1. The Westway highway project was staunchly opposed because it was exorbitantly expensive. To add insult to injury, the plan could be "traded-in" for money from the feds to help with other non-road building expenses such as the much needed subway/mass-transit aide. What do you understand the word "trade-in" to mean? Is this quote implying that if the Westway project were to be "traded-in" for mass-transit aide it may be impossible to collect?
2. How do you interpret the last sentence? Is the Federal government being stingy with revenue? Or is it that the general funds are already overloaded by $5.7 billion and somehow they're only manage to dole out $800 million a year?

(*) For those who don't know, Westway was a series of proposed plans to improve the state of the Joe DiMaggio Highway (or West Side Highway).

Answer 1

This quote appears to have been written in 1982. Under normal circumstances, the US's Highway Trust Fund gets all its money from gasoline sales taxes. However, in 1982 the amount hadn't been raised in nearly 30 years. This amount was clearly no longer sufficient, as congress at the end of that year felt the need to essentially double it.

I'm not familiar with the "trade-in" provisions, but according to the linked text, it looks like they were more of an uncodified practice rather than a part of the law. In other words, you go to Congress and say you'd like to take your portion of federal highway funds in cash, then if Congress approves, they pass a law giving you the money (from general funds), leaving the trust fund alone.