it's politics

The TEA programs are political. While the Feds have set out general guidelines its the States that implement the program. The money can be used for bike trails, highway landscaping, bus stop improvements (cover for benches to rehabing a building as a transit center).
In California it is allocated by the local county transporation commissions. I know of one county that took a look at all of the applications for projects and then ranked then so that every local jurisdiction got some money.
When you try to keep everyone happy no one gets a big serving from the pot.