The picture below is essentially what the track looks like.
well, uh
why not take a picture of the actual track?
other thoughts ...
In Blockland, when you hit a wall, you tend to come to a complete stop. ...Since this is a road circuit, these things don't really apply, but they're something to consider if you make a track: Instead of putting up walls that mercilessly punish those who get too close to the apex, you could have speed bumps. Cutting the corner too much would slow you down, but going over a little bit would just make the car a bit unstable. Excessive corner-cutting could be stopped with walls in the right places, but right now, with your corner that has a tire wall on the inside, there's an extremely fine line between hitting the apex or crashing, losing all of your speed. At the very least, there might be some way to make that a steep curb which would tilt the car, effectively pushing away those who took it too close, without wrecking them.
I guess the main problem for me is that it's possible to take this track almost flat-out (as you say). This is a problem with the cars, rather than the track. And, of course, this is subjective. Other people prefer that blockland cars turn and stop with extreme precision... I prefer cars where you need to use the brakes, or at least lift off, to get around a corner effectively. Cars should have weight, and punish recklessness... and recklessness should be more than simply pointing the wrong direction and hitting the walls. I think that taking a corner too fast should make you slide a little, and it should be possible to lose control. If that was the case, then even with wider roads, or on a circuit with lots of run-off, it would require skill to get around as fast as possible. The possibility for losing control makes staying in control that much more exciting, and making a great lap feels like an achievement.
On the topic of both loss of control and speed bumps, there seems to be a way that a car could maintain grip while on a flat surface, but start sliding after it goes over bumps, requiring the driver to either slow down or spin out.
I suspect my problems are too big for the scope of what you're going for, so don't take it as criticism so much as general thoughts about racing.