As I was driving in the left lane of a four lane local road. I passed over a small hump in the road. The suspension lifted and as it settled. I lost control of the steering and the truck abruptly pulled left. I managed to gain control and guide the truck from collision with another vehicle and the bridge guard rail. I had no warning lights and the truck drove straight at the time. Tire wear was normal and I had an appointment in three days for new ties and alignment since I did hear a clunk a few days earlier.