Burnout CRASH!

My advice is to get this achievement in Rush Hour on Rockham and 2nd (14th intersection) as this is one of the objectives you have to complete to get all the stars in this junction.

I think there are a few possibilities to achieve this but what I've done (and what seemed easier to me) was take the left path and stick to the right side of the wall, smashing street lights and other objects until the garbage cans at the end of the path. Then, stick to the left until you smash against the car besides the 3 trash dumpsters.

If done correctly, you should have at least the required 15x smash chain.

I had trouble following the first solution and the other solution offered a way, that while clearly done by the author, was hard for me to replicate.

So after many tries using their methods (or what I believed to be their methods) and using many different kinds of cars, I went to youtube. Below is a 22 second video that shows the achievement. After watching their clip, I did it in two tries. It's not my clip, I take no credit. Here's a text version in case you prefer:

Go to Rockham and 2nd as you need to get a 15x smash chain for one of the stars anyway, so you might as well kill two birds with one stone. Choose your largest vehicle (the one all the way on the right). One integral thing to keep in mind as you do this is that in order to keep a chain 'going', you must constantly be hitting things (e.g., you can't have too long a delay between hits). If you're not sure yet what a smash chain is, it means running your car into objects. A key part of this is that you need to smash your car into an 'accepted' item / vehicle at the end in order to register the chain, otherwise the game tells you that you failed to hit the traffic. We'll get to that.

Once loaded, Go down the left-most alley. You'll want to just hold your stick to the left immediately so you start turning.

Ideally you want to take out as many 'pieces' of that fence as you can, so you'll want to almost hit them in an 'upwards' fashion and/or take out the lightpost right before them. You'll want to end at the 'top' or right side of the wall so you're going into the next thing.

Hug the wall on the right as you do this. You'll want to take out the lightpost and the little umbrella thing. Stay on the right and take out the little garbage can and the lightpost that come up ahead of you. Swerve left and take out the lightpost in the middle (integral to keeping your chain going). Keep left and take out the two trashcans next to each other right along the left wall. Continue along the left wall to take out the lightpost.

Finally, crash into the two yellow boxes. From there, simply crash into the shed, ideally so that the back of your truck also hits the bigger building to its left as it may count towards the chain as well. It's important you crash into the shed as it counts as having 'hit traffic' (and the game doesn't tell you you failed to do that). Sometimes it may still tell you this - don't be discouraged, just try again, knowing that it works.

Let's count how many items I said above. Assuming you hit at least 3 of the pieces of fence, the 1 lightpost before them, the 1 lightpost, the 1 umbrella, the 1 garbage can, the 1 lightpost, the 1 middle lightpost, the 2 trash cans, the 1 lightpost, and the 2 yellow boxes, and the shed at the end, you'll have a 15x smash chain.

You're going to get discouraged at some point. Don't be discouraged. In case you're a video watcher instead of text (which I recommend regardless), see the video below. This is proof that this method works. In addition, it worked for me, just last night. If you do feel the need to downvote, make sure you at least leave a comment about what worked better for you so others can benefit!

Here's a video I made on how I got the achievement. Unfortunately, the capture turned out not to be recording when it popped, so you'll have to settle with a star.

In the video, I show you how I did it, then take you back to the beginning and walk you through step by step. Please be aware that a guide can only go so far for this achievement. This is easily the hardest achievement in the game, next to Burnout Crash All-Star of course, and it will still probably take you several tries to get it. Good luck!