Once you reach the part of the story where you have the tire iron and the bridge has gone out, you will be at the truck crash with the fertilizer (Alternatively if you have left the area, you just need to travel down Highway 9 until you can stop at the crash site). First use the tire iron on the wheels. Then use your hands on the back of the trailer. Ben will walk behind it. At this point kick it and the trailer will topple. Now proceed back on Highway 9 toward the mink farm. When you reach there, Nestor and Bolus will be waiting there in their car. They will begin pursuit. Just continue driving down Highway 9. When you reach the trailer crash site, a short cutscene will begin. Nestor and Bolus will crash. As the limo approaches in the cut scene, the achievement will pop.