Fun idea, but the game is way to difficult. You have very little time to built a road before the car has reached you. So you quickly start panicking. It is also difficult to plan ahead, because there seem to be too many different kinds of pieces. Classic Tetris gets away with a single piece preview, because you can leave space for possible pieces, since there are only 7. But there are way to many to have spots for things, as well as little time to waste dumping unneeded roads to dig for a piece you need.

Generally speaking, as a game designer you are way better at your game then anyone else. So if something is a challenge for you, then it is too hard for your players. Especially with a game jam game, where people only want to spend some five minutes playing your game, before moving onto the next one.

Hopefully you had a lot of fun making this, and good luck on any future projects.