I'd have made sure everyone was OK, used my cell phone camera to take pictures of skid marks on the road, if they existed, and of the collision. Hiding the weed away from the car is a good idea that I wouldn't have thought of (because I wouldn't have been carrying any), but if I had, I'd have probably had it already buried deep inside the trunk and wouldn't have been prudent enough to move it. I'd make darn sure I smelled and acted as sober/free of influence as possible and as cool as relaxed as possible. I'd have exchanged insurance, driver's license numbers, license plates and telephone numbers with the other party. I'd have avoided admitting guilt even if I were guilty. Then I'd have waited for the cops to come in the car where it was warmer and hoped for the best.